op phys 1 Flashcards

Question

25.Which of the following are methods of heat transfer (A) Convection (B) Evaporation (C) Revolution (D) Thermal Expansion

Answer 1

(A) (SSC CGL 2016) Exp: Convection - It is the process of heat transfer in a gas or liquid by circulation of the currents downwards to upwards.

Answer 2

(D) Exp: Thermopile is a set of thermocouples arranged for measuring small quantities of radiant heat.

Answer 3

(A) (SSC LDC DEO (2011) Exp: Evaporation - Liquid into Gas Sublimation - Solid into Gas Freezing - Liquid into Solid Melting - Solid into Liquid Thermodynamics

Answer 4

(B) (SSC CHSL 2011) Exp: Because white clothes reflect the whole light and do not absorb any heat radiation.

Answer 5

(A) Exp: E = hn E = Energy of a photon h = planck's constant n = frequency of the radiation [J] = h[s-1] [h] = Js

Answer 6

(B) Exp: Angular Momentum= Perpendicular Distance × momentum = [L] [MLT-1] [ML2T-1] = dimension of planck's constant.

Answer 7

(A) (SSC CGL 2014) Exp: Inner surface of the glass will expand more than the outer surface.

Answer 8

(A) (SSC CPO 2015) Exp: The First Law of Thermodynamics states that total energy of an isolated system is constant. DQ = DU + DW DQ = Heat absorbed DU = Change in internal energy DW = Work done by the system

Answer 9

(A) Exp: At low pressure and high temperature, Real gas can act as ideal gas as intermolecular force of attraction is negligible.

Answer 10

(B)Exp: White surface does not absorb any incident radiations that fall on it. It reflects all the incident radiation.

Answer 11

(B) (SSC (10+2) LDC & DEO 2015) Exp: Bursting of cycle tyre is considered as an adiabatic process because it happens suddenly without any time for heat exchange.

Answer 12

(B) (SSC M.T.S 2013) Exp: This is according to the Wien's displacement Law, Higher the temperature, lower is the wavelength.

Answer 13

(D) (SSC 10+2) DEO & LDC 2013) Exp: A blackbody is a body that absorbs all incident radiations falling on it regardless of the frequency and wavelength of the radiation.

Answer 14

(A) (SSC CGL 2004) Exp: Air on getting warmer rises up. This air is trapped by cooling unit on the upward side and made cool.

Answer 15

(B) (SSC CGL 2004) Exp: Refrigerator consists of devices that Compress and expand refrigerant gas. When gas is compressed it expels heat and when it is expanded, it absorbs heat. Thereby produce cooling.

Answer 16

(D) (SSC Constable 2013) Exp: Black colour absorbs all the radiations that falls on it. Hence, to supply more heat to the food in the utensil they are kept black. Temperature

Answer 17

(B) Exp: The S.I unit of temperature is Kelvin (K).

Answer 18

(B) (SSC CHL 2013) Exp: Because at 4ºC, the density of water is maximum and volume of water is minimum.

Answer 19

(B) (SSC CAPF 2016) Exp: According to Newton's Law of Cooling, the rate of loss of heat from a body is directly proportional to the temperature difference between the body and its surroundings.

Answer 20

(B) (SSC CGL 2016) Exp: T(°C) = 5 {[T(F)]- 32}× 9 T°(C) = (32 - 32) × 5 9 T°(C) = 0°C

Answer 21

(B) (SSS MTS 2006) Exp: F = 9 5 C + 32 Let us say F = C C = 9 5 C + 32 - 32 = 4 5 C C = - 40 i.e. at - 40 both Fahrenheit and Celsius scale show same reading.

Answer 22

(C)Exp: Pyrometer is a device that measures temperature of a surface of the spectrum of thermal radiation from a distance.

Answer 23

(C) (SSC CGL 2006) Exp: To measure very high temperature thermo-electric pyrometer is used because it can measure 200ºC to 1660ºC

Answer 24

(C) (SSC CGL 2016) Exp: Metals have higher coefficient of thermal conductivity than plastic. So, Metal conducts heat away from our body. But as plastic is an insulator, it will not do so.

Answer 25

(B) (SSC CGL 2016) Exp: 0 K is absolute zero i.e., the lowest possible temperature. At absolute zero all molecular motion cease and the molecules have minimum kinetic Energy. 0 K = - 273.16°C

Answer 26

(A) (SSC-CHSL 2015) Exp: Because freezing point of alcohol (- 114.1°C) is very low. So, alcohol thermometer can be used to measure very low temperature.

Answer 27

(B) (SSC-CHSL 2012) Exp: Lapse Rate - The rate at which atmospheric temperature decreases with an increase in altitude. Temperature Inversion - It is when atmospheric temperature increases with increase in altitude, hence it is negative Lapse Rate.

Answer 28

(D) Exp: Adiabatic demagnetization is a process of cooling. The principle is that when some materials (rare earth elements) are placed in magnetic field they heat up and get cool down when removed from the magnetic field.

Answer 29

(A) (SSC CGL 2016) Exp: Absolute zero is 0 K. It is the lowest possible temperature. At 0 K, all molecular motion cease and molecules have minimum kinetic energy.

Answer 30

(B) (SSC CGL 2016) Exp: On supplying heat, atoms of the substance begin to vibrate due to increased kinetic energy.

Answer 31

(A) (SSC LDC & DEO 2013) Exp: Gas molecules have larger coefficient of expansion than liquid. Hence for a small amount of heat, they show greater volatility.

Answer 32

(C) (SSC CGL 2010) Exp: Heat flows from a body at a higher temperature to a body at lower temperature. As both ice and water are at 0°C. Therefore, no heat flow will take place, hence no change will happen.

Answer 33

(C) (SSC CHSL (2011)) Exp: The higher the pressure inside a boiler, the higher the temperature of boiling water.

Answer 34

(A) (SSC Tax. Asst. 2007) Exp: Sling Psychrometer consists of two thermometers mounted together with a handle attached on a chain. Freezing Point and Boiling Point

Answer 35

(A) Exp: Triple point - The temperature and pressure at which a substance can exist in equilibrium in the solid, liquid and gaseous state. The triple point of pure water is 0.01ºC (273.16 K).

Answer 36

(C) (SSC CGL (Tier-I) 2014 Exp: The freezing point of a liquid is the temperature at which a liquid changes its state to solid. The freezing point of water is 0ºC.

Answer 37

(C) (SSC FCI 2012) Exp: Ice being a poor conductor of heat, it does not allow atmospheric cold to reach below it. Hence, keeping the water underneath at 4ºC.

Answer 38

(B) (SSC CGL 2012) Exp: With increase in altitude, atmospheric pressure decreases. So, the boiling point decreases. As boiling point is directly proportional to the pressure.

Answer 39

(B) (SSC MTS 2014) Exp: Clouds are made up of tiny water droplets which have very low density, which makes them very light. This is why clouds float in atmosphere.

Answer 40

(D) (SSC CHSL 2015) Exp: Soldering is the process by which two metals are joined together. Cohesion is the property of material due to which its molecules stick together.

Answer 41

(A) Exp: On freezing water expands. Thus on expanding the water exerts pressure on the pipe from inside and thus pipe gets busted.

Answer 42

(A) (SSC CGL 2012) Exp: Inside a pressure cooker, pressure is high which increases the boiling point of water, thereby decreasing time for cooking.

Answer 43

(C) (SSC Steno. 2011) Exp: If humidity is 100%, water will not get evaporated as air is already saturated with moisture.

Answer 44

(D) (SSC CGL 2002) Exp: When heated from 0° to 100°C volume of a given mass of water will first decrease and then will increase. This is because of anomalous expansion of water, till 4°C the water will attain maximum density and then decreases. For a given mass, density is inversely proportional to volume. Thus volume will first decrease and then will increase.

Answer 45

(A) (SSC CGL 2016) Exp: Adding salt raises the boiling point of water, this allows food to get cooked at higher temperature. The higher the temperature, the higher the rate of heat transfer between food and water, thus food gets cooked more quickly.

Answer 46

(A)Exp: On increasing pressure, boiling point increases. On decreasing pressure, boiling point decreases.

Answer 47

(A) (SSC Constable 2015) Exp: At 4°C water reaches its maximum density. As it approaches, the freezing point there is a decrease in its density.

Answer 48

(C) (SSC CGL 2016) Exp: Supercooling is the process of cooling of a liquid below its freezing point without undergoing solidification or crystallization. Miscellaneous

Answer 49

(A) (SSC DEO 2009) Exp: At low temperature germs can not multiply and thus become non-reactive.

Answer 50

(B) (SSC CGL 2005) Exp: Cryogenics is the branch of physics which deals with the production and behaviour of materials at very low temperature.

Answer 51

(A) (SSC CGL 2014) Exp: The colour of star depends on its surface temperature, as at dry temperature stars emit frequencies of different colour.

Answer 52

(D) (SSC CPO 2009) Exp: According to Newton's law of cooling, the rate of cooling of an object for a given area depends upon the temperature difference between the body and the surroundings. Conductors are bettter Radiators. More the area, higher will be the rate of cooling.

Answer 53

(A) (SSC Matric Level 2011) Exp: Metal expands on heating, the hole will expand in the same ratio in which the metal expands.

Answer 54

(C) (SSC Combined Matric Level 2002) Exp: The fan circulates air. When the moving air comes in contact with our perspiration it carries away the heat from our skin and thus produces cooling.

Answer 55

(A) (SSC Matric Level 2002) Exp: Wind and Ocean currents are example of convection currents.

Answer 56

(C) (SSC CGL 2000) Exp: Rate of cooling is directly proportional to the surface area of body through which heat is transferred. For same volume, sphere has minimum area and circular plate has maximum area. So, sphere will have slowest rate of cooling and circular plate will have maximum rate of cooling.

Answer 57

(D) SSC Steno (Grand C & D) 2010 Exp: Thermocouple is a device which converts incoming heat radiations (heat energy) into electrical energy.

Answer 58

(A) (SSC Matric Level 2000) Exp: Water content inside frozen foods converts into steam on heating. Holes are picked in the pouch to allow steam to escape.

Answer 59

(C) (SSC Investigator 2010) Exp: On a clearer night, there are no clouds to reflect heat back to the earth's atmosphere. So heat escapes from the atmosphere. But on a cloudy night, clouds trap the heat and reflect back the heat which try to escape from the atmosphere.

Answer 60

(B) (SSC CHSL 2015) Exp: Insolation - It is the amount of solar radiation reaching to the earth's surface in a given area.

Answer 61

(C) (SSC CGL 2016) Exp: Desert coolers are based on the principle of evaporative cooling. Water gets evaporated by taking heat from the surrounding air. Thereby reducing the temperature of surroundings, which produces cooling effect.

Answer 62

(D) (SSC CHSL 2011) Exp: Geothermal energy is the heat generated and stored inside the earth's surface.

Answer 63

(C) (SSC Matric Level 2002) Exp: In summer the metal expands. In winter the metal contracts. Since the expansion in metallic rails is lengthwise, it is termed as Linear expansion

Answer 64

(C) (SSC Matric Level 2002) Exp: Diesel engines use the heat of compressed air to ignite the fuel. The work done on gas to compress it gets converted to its internal energy and thus temperature gets raised.

Answer 65

(C) (SSC Matric level 2002) Exp: Mud is a bad conductor of heat. In summer the outside heat can not enter the house and in winter inside heat can not flow outside.

Answer 66

(C) (SSC CGL 2014) Exp: Relative humidity is the ratio of water vapour density to the saturation water vapour density and expressed in percentage Relative Humidity = Actual vapour Density Saturation Vapour Desnsity ×100

Answer 67

(B) (SSC Combined Matric Level 2002) Exp: Woollen cloths are a poor conductor of heat, hence do not allow body heat to escape outside.

Answer 68

(B) (SSC Combined Matric Level 2002) Exp: The four stroke petrol engine is based on Otto cycle. The cycles are. (i) Intake stroke (ii) Compression stroke (iii) Expansion stroke (iv) Exhaust stroke

Answer 69

(C) (SSC Combined Matric Level 2006) Exp: Water has high specific heat which allows water to draw up more heat from the radiator and hence keeps it cool.

Answer 70

(C) (SSC Combined Matric Level 2006) Exp: The heat required to convert 1 gm of ice at 0°C into 1 gm of water at 0°C is called as Latent Heat of Fusion. It is 336 J for ice to water.

Answer 71

(B) (SSC Combined Matric Level 2008) Exp: When phase of water is changed from liquid to vapour, heat energy gets stored, which is known as Latent heat of vapourization.

Answer 72

(B) (SSC DEO 2008) Exp: The condition when vapour pressure of liquid is equal to the atmospheric pressure is termed as Boiling. Hence at that temperature the liquid boils.

Answer 73

(D) (SSC MTS 2013) Exp: Specific gravity is the density of any substance relative to the density of water at 4°C.

Answer 74

(B) (SSC CGL 2015) Exp: Heat budget is the balance between incoming solar radiation and the heat radiation emitted back by earth. Any unbalance in this, makes the earth warmer or cooler.

Answer 75

(A) (SSC CGL 2016) Exp: Lower the boiling point higher is the volatility. Alcohol has boiling point 78°C whereas boiling point of water is 100°C.

Answer 76

(C) (SSC CGL 2016) Exp: Temperature remains constant at boiling point because the extra heat added is utilized as Latent heat of vapourization to change the phase of liquid to vapour.

Answer 77

(C) (SSC CPO 2017) Exp: Radiation- The energy is transferred in the form of waves. No medium is required for radiation. On a clearer nights, there are no clouds to reflect heat back to the earth's atmosphere. So, heat escapes from the atmosphere.

Answer 78

(D) (SSC CPO 2017) Exp: Direction of heat flow depends on temperature. Heat always flows from a body at higher temperature to a body at a lower temperature.

Answer 79

(B) (SSC CPO 2017) Exp: Mercury thermometer is based on the principle that liquids expand when heated and contract when cooled. So, when the temperature increases, the mercury expands and rises up in the tube and when the temperature decreases it contracts and falls down in the tube.

Answer 80

(A) (SSC CPO 2017) Exp: First Law of Thermodynamics is a version of the Law of Conservation of Energy. This law states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but can neither be created nor be destroyed.

Answer 81

(C) (SSC CPO 2017) Exp: At 373K (100o C) temperature water converts to water vapour.

Answer 82

(C) (SSC CGL 2017) Exp: Glass is a bad thermal conductor because in glass there is no flow of electron. So, it doesn't conduct heat. It is also bad conductor of electricity.

Answer 83

(A) (SSC CGL 2017) Exp: Pyrometer is the device used for measuring relatively high temperatures such as are encountered in furnaces. Pyrometer works on the principle of sensation of heat radiation.

Answer 84

(A) (SSC CGL 2017) Exp: Pure water freezes at 32 Fahrenheit,0 degree Celsius, 273.15 Kelvin. T(Fº) = T(ºC) × 9 5 + 32

Answer 85

(A) (SSC CGL 2017) Exp: S.I. unit of temperature is Kelvin (K) named after Lord Kelvin. The Kelvin is defined as the fraction 1 273.16 of the thermodynamic temperature of the triple point of water (exactly 0.1ºC or 32.018ºF)

Answer 86

(A) (SSC CGL 2017) Exp: The centigrade scale was invented by Swedish Astronomer Anders Celsius (1701-1744) has 100 degrees between the freezing point (0ºC) and boiling point (100ºC) of pure water at sea level air pressure.

Answer 87

(A) (SSC CGL 2017) Exp: The temperature when both are equal by given below equation:- Formula:- ºC = 9 ºC 32 5 9 ºC-ºC 32 5 -4 ºC 32 5 5 ºC -32 4 ºC = - 40 9 ºF ºF 32 5 9 ºF - ºF 32 5 -4 ºF 32 5 5 ºF -32 4 ºF = - 40 So, the temperature when both the Celsius and Fahrenheit Scales are the same is -40 degrees.

Answer 88

(D) (SSC CGL 2017) Exp- Same as Q. No. 109

Answer 89

(C) (SSC CGL 2017) Exp: Melting point of a solid is the temperature at which it changes its state from solid to liquid at atmospheric pressure. For ice, Melting point of ice is 0ºC or 273K.

Answer 90

(C) (SSC CHSL 2013) Exp: The particles execute a clockwise motion i.e. updown as well as to and fro. Hence, both tranverse and longitudinal waves are produced.

Answer 91

(B) (SSC MTS 2014) Exp: An oscilloscope is an instrument which displays the electronic signal in the form of waveforms on a screen.

Answer 92

(B) (SSC Sec. Officer (Audit) 1997) Exp: In frequency modulation, the frequency of the signal is varied whereas amplitude (dimension) is kept constant.

Answer 93

(B) (SSC Matric Level 2002) Exp: Sound wave is a longitudinal wave. Hence it requires a material medium for its propagation. Hence, it can not travel in vacuum.

Answer 94

(D) (SSC CGL 2013) Exp: A stationary wave is formed by superposition of two waves having same amplitude and frequency but are moving in opposite direction.

Answer 95

(B) (SSC CGL 2016) Exp: Intensity of a wave is proportional to the square of its amplitude, i.e. Intensity Amplitude2. EM Waves

Answer 96

(D) (SSC CGL 2016) Exp: X-rays are produced when electrons strike metal target. While in photoelectric effect electrons are emitted when incident radiation of suitable frequency falls on a metal target.

Answer 97

(D) (SSC CGL 2016) Exp: ultrasonic waves are sound waves. As sound waves are longitudinal waves, they cannot be polarized because longitudinal waves cannot be polarised.

Answer 98

(C) (SSC CGL 2016) Exp: The electromagnetic radiation is classified into Radio wave, Microwave, Infra-red wave, Visible light, Ultraviolet wave, X-rays and Gamma rays on the basis of wavelength.

Answer 99

(A) (SSC CGL 2016) Exp: The electromagnetic spectrum is in order of increasing frequencies: Radiowaves, Microwaves, Infrared waves, Visible Light, Ultraviolet waves, X-rays and Gamma Rays.

Answer 100

(C) (SSC CGL 2016) Exp: All hot object emits Infrared radiation. This radiation cannot be seen with naked eyes but can only be felt in form of heat.

Answer 101

(A)Exp: X-rays have high penetrating power as they can penetrate through spine and heel taking images of bones.

Answer 102

(C) (SSC CGL 2016) Exp: When an electron jumps from higher energy state to the ground state (n = 1) The series of spectral lines emitted are called Lyman series and it is in Ultraviolet region.

Answer 103

(B) (SSC CGL 2015) Exp: Speed of light in any medium is directly proportional to the wavelength of light. As violet has minimum wavelength, So its speed is minimum.

Answer 104

(C) (SSC CGL 2015) Exp: X-rays are high energy EM-waves, with very short wavelength. The x-rays consists of neutral particles called photons.

Answer 105

(D) (SSC CGL 2014) Exp: Rads refer to radiation absorbed doses. It is the amount of energy carried by radiation that gets absorbed by body tissues.

Answer 106

(D) (SSC CGL 2014) Exp: Transition ions absorbs light in visible region and also reflect some visible spectrum. For example: Cu (II) absorbs entire light in visible spectrum execpt blue hence it appears blue.

Answer 107

(C) (SSC MTS 2014) Exp: The Infrared rays of the sunlight are the component responsible for heating. The Green house effect is the phenomenon of heating up of the earth's atmosphere by sunlight.

Answer 108

(B) (SSC CAPFs and CISF 2013) Exp: The E.M. wave spectrum in order of decreasing wavelength is as follows Radiowaves, Microwaves, Infrared, Visible, U.V., X-rays and γ Rays.

Answer 109

(C) (SSC CAPF CISF 2013) Exp: Photoelectric effect is the phenomenon of emission of electron when a light of suitable frequency falls on metal surface. Here the photon (Particle) transfers its energy to electrons.

Answer 110

(A) (SSC CHSL 2013) Exp: Matter waves are de-Broglie waves. Matter waves are the waves which show dual nature. They behave like particle and travel like waves.

Answer 111

(C) (SSC CHSL 2013) Exp: Microwaves have short wavelength and high frequency, hence they pass through earth's atmosphere and can reach to satellite easily.

Answer 112

(B) (SSC Matric Level 2002) Exp: Flourescent tube emits ultraviolet radiation. Due to this flourescent tubes cause various health risk to hum

Answer 113

(C) (SSC CHSL 2013) Exp: Radio waves are used for long distance wireless communication. They get transmitted from sender, gets reflected by ionosphere and thus reaches to reciever.

Answer 114

(D) (SSC Sec. Officer 2001) Exp: Ozone layer is composed of O3 molecules which absorbs harmful U.V rays coming from the sun hence they cannot penetrate earths atmosohere

Answer 115

(A) (SSC CPO 2002) Exp: Gamma rays can cause gene mutation which is the alternation in the sequence of DNA.

Answer 116

(A) (SSC Sec. Off. 2002) Exp: Energy of E.M. radition directly proportional to the frequency. Higher the frequency, higher will be the energy. Order of energy for given options is: Space rays > Gamma Radiation > X rays > UV rays > Infrared radiation.

Answer 117

(C) (SSC CGL 2013) Exp: U.V. light acts as disinfectant by changing the DNA pattern of bacteria in water so that they can't multiply.

Answer 118

(B) (SSC CGL 2013) Exp: Bragg's spectrometer is used to measure the wavelength of X-rays. It operates on the principle of diffraction.

Answer 119

(C) Exp: RADAR refers to Radio Detection and Ranging. RADAR uses radiowave to detect and locate distant objects.

Answer 120

(D) Exp: A.H. Taylor and Lio C. Young are credited with the invention of RADAR.

Answer 121

(A) [SSC Tax. Asst. 2009] Exp: William conrad roentgen discovered X-rays.

Answer 122

(A) Exp: a-rays have the least penetrating power it can even be blocked by a piece of paper. - rays can pass through aluminium foil. - rays can even pass through lead box. X - rays can penetrate human body and are thus used to create image of bones.

Answer 123

(A) (SSC CGL 2002) Exp: By studying the X-rays diffraction pattern of precious stone, defects can be detected.

Answer 124

(B) (SSC CPO 2005) Exp: The visible region lies in the wavelength range of 3900 Å - 7800Å.

Answer 125

(B) (SSC CHSL 2013) Exp: In a filament type light bulb only 2% - 4% energy is converted to visible light where as more than 95% energy is wasted as heat in the form of infrared light.

Answer 126

(D) (SSC FCI 2012) Exp: MRI stands for magnetic resonance imaging. It uses magnetic waves to form image of internal body org

Answer 127

(A) (SSC CHSL 2005) Exp: Frequency = Velocity wavelength = 300 0.3 = 1000 Hz Since, Audible frequency range is 20 - 20,000 Hz. Hence, the given wave will be audible in nature.

Answer 128

(B) (SSC Tax. Asst. 2009) Exp: Bolometer is an instrument used for detecting heat or electromagnetic radiation. It is used in thermal cameras, to detect forest fires, etc.

Answer 129

(C) (SSC CGL 2002) Exp: Coolidge tube is a vacuum tube which is used in the production of X-rays. X-rays are high energy EM waves.

Answer 130

(C) (SSC Tax Asst. 2004) Exp: Infra Red component of white light is responsible for heating. Thus it is Infra-Red waves which make solar cooker heat up.

Answer 131

(B) (SSC CPO SI 2005) Exp: Spark plug in vehicle emits electro magnetic waves and they interfere with electromagnetic waves of T.V receiver, antenna and create disturbances. Due to this T.V reception gets distorted.

Answer 132

(A) (SSC Sec. Officer 2005) Exp: Mesons are found in cosmic rays. Mesons are subatomic particles which are very unstable.

Answer 133

(D) Exp: AM stands for amplitude modulation. It is used in electronic communication in which amplitude of the carrier waves is modulated according to the modulating signal.

Answer 134

(B) (SSC CISF ASI 2010) Exp: Heinrich hertz first sent electromagnetic waves to distant places. Electromagnetic waves are used to transmit signals to T.V., telephone etc.

Answer 135

(C) (SSC Asst. Grade 2011) Exp: Gamma rays and X-rays have various similarities like both travel at the speed of light, both have high energy photons and both are the forms of electromagnetic waves.

Answer 136

(B) (SSC Matric Level 2002) Exp: Audio signals of TV are frequency modulated. Audio signals have frequency in the range of 20 Hz to 20,000 Hz. This is also the limit of human hearing.

Answer 137

(B) (SSC Matric Level 2002) Exp: Tape recorder works on the principle of magnetic field. So if it will be kept near magnet, the magnetic field of magnet and tape will interfere and cause problem in working of tape recorder.

Answer 138

(B) (SSC Matric Level 2002) Exp: Fog, mist, clouds and darkness are transparent to Infrared radiation.

Answer 139

(A) (SSC Matric Level 2002) Exp: Documents that are authentic, will glow when illuminated by Ultraviolet radiation.

Answer 140

(D) (SSC Delhi Police SI 2012) Exp: Remote control of the television make use of infrared waves to send signals. Infrared radiation is a kind of invisible light and human eye cannot detect it.

Answer 141

(C) (SSC MTS 2013) Exp: Electromagnetic spectrum includes waves from longer wavelength to shorter wavelength. γ -rays are placed at the end of electromagnetic spectrum having shortest wavelength. Simple Harmonic Motion

Answer 142

(D) Exp: A seconds pendulum is a pendulum whose time period is 2 sec, one second for swing in one direction and one second for the return swing.

Answer 143

(A)Exp: Periodic motion is the motion which repeats itself after a regular interval of time. eg. motion of pendulum of clock.

Answer 144

(D) (SSC CPO 2017) Exp: Gamma-rays has the highest frequency. The order of increasing frequency:- Radio waves < Micro waves < Infrared waves < Gramma-rays.

Answer 145

(B) (SSC CPO 2017) Exp: Radio waves are used for communication in artificial satellites. Radio waves have lower frequencies and lower wavelengths than microwaves. Hence, they are used to transmit signals to television and radios.

Answer 146

(C) (SSC CPO 2017) Exp: The distance between consecutive crests is one wavelength and the distance between a crest and a consecutive trough in a transverse wave is half of the wavelength.

Answer 147

(A) (SSC CGL 2017) Exp: Electromagnetic waves do not show interference and diffraction.

Answer 148

(C) (SSC CGL 2017) Exp: Time Period is the time taken by the pendulum to make one complete oscillation. It is represented by the letter T.

Answer 149

(D) (SSC CGL 2016) Exp: Components of light get scattered in the atmosphere. Red having the largest wavelength does not get scatter much. Therefore sun appears red in colour at sunrise and sunset. Scattering is inversely related to wavelength. Red having maximum wavelength is scattered least and hence reaches our eye.

Answer 150

(D) (SSC CGL 2016) Exp: When the sunlight falls on the ocean, components with longer wavelength (red, orange and yellow) are absorbed more strongly by water than shorter wavelength components (blue). So it is blue light that gets returned/scattered.

Answer 151

(D) (SSC CGL 2016) Exp: In the absence of the earth's atmosphere, sky will appear black because there are no particles present to scatter light.

Answer 152

(D) (SSC CGL 2016) Exp: Transverse nature of light wave means the direction of oscillation of light particles is perpendicular to the direction of propagation of light. The Phenomenon of restricting the oscillation of a wave to just one direction in the transverse plan is called as Polarization.

Answer 153

(B) (SSC CGL 2015) Exp: Rainbow is formed by dispersion, refraction and total internal reflection of light in the water droplet.

Answer 154

(D) (SSC CGL 2016) Exp: The smaller the wavelength the larger will be the deviation (refraction). As the red light has largest wavelength, it deviates the least.

Answer 155

(D) (SSC CHSL 2014) Exp: White light on getting dispersed in its seven constituent components undergo refraction and total internal reflection which results in the formation of a rainbow.

Answer 156

(D) (SSC CHSL 2016) Exp: Polarization means transforming vibrations in a single plane. All other waves except light wave are in single plane. Hence only light waves can be polarised.

Answer 157

(A) (SSC CGL 2014) Exp: Because air molecules scatter blue light from the sun more than they scatter red light. This scattering of light by particles in a medium without any change in wavelength is called Rayleigh scattering.

Answer 158

(D) (SSC CGL 2014) Exp: The splitting of White Light into its constitutent seven colours is called dispersion of light.

Answer 159

(A) (SSC CGL 2013) Exp: Colloidal solution:- It is a kind of solution in which size of solute particles (10-7 cm and 10-5) is bigger than that of a true solution. Colloidal solution have minute particles that scatters light and the scattering of light by colloidal solution is called Tyndall effect.

Answer 160

(B) (SSC Sec. officer (Audit) 1997) Exp: During rainbow formation, sun remains behind the observer and its light passes from the raindrops, it refracts and gets totally internally reflected into 7 different colours called rainbow.

Answer 161

(C) (SSC Tax Assistant, Income Tax & Centre Excise) 2009) Exp: Soap bubble shows interference pattern because the reflected light from inner and outer layer is superimposed to create interference pattern.

Answer 162

(C) (SSC CGL 2015) Exp: Rainbows are formed when sun light diffracts, refracts and totally internally reflect by water droplets present in atmosphere.

Answer 163

(D) (SSC Steno. C, D 2012) Exp: As red light deviates the least it is at the outermost place and the violet with minimum wavelength is at the innermost place. The sequence of Rainbow is as follows ROYGBIV.

Answer 164

(C) [SSC CGL 2014] Exp: Oily films show colour patterns because light which gets reflected at air- oil film and oil-water film interfere and thus coloured patterns are formed. Reflection

Answer 165

(A) [SSC Matric Level 2006] Exp: An optically plane surface reflects a beam of light in a single direction owing to the laws of reflection.

Answer 166

(B) (SSC CAPFs SI 2016) Exp: Land covered with fresh snow reflects more sunlight because white and smooth surface are best reflectors.

Answer 167

(D) (SSC CGL 2016) Exp: Optical fibers work on the principle of total internal reflection as light ray tries to go from glass to air.

Answer 168

(D) (SSC CHSL 2015) Exp: Mirage is an optical illusion such as the appearance of a sheet of water in a desert or in which distant objects are seen inverted. It is formed by refraction and total internal reflection.

Answer 169

(A) (SSC CAPF SI, CISF 2015) Exp: Total internal reflection is a phenomenon that occurs when light travels from denser medium to rarer medium such as glass to air or water to air.

Answer 170

(D) (SSC CHSL 2014) Exp: Optical fibre works on the principle of Total Internal Reflection. Light travels great distance without undergoing attenuation inside the fibre.

Answer 171

(B) (SSC CHSL 2010) Exp: Owing to Fresnel's equation, the larger the incident angle, larger will be the energy in reflected light.

Answer 172

(B) [Tax Asst Exam 2006] Exp: Diamonds are cut in such a way that light undergoes total internal reflection multiple times and thus diamond sparkles. Refraction

Answer 173

(C) (SSC CGL 2016) Exp: Refraction is the change in direction of light on passing from one medium to another.

Answer 174

(A) (SSC CHSL 2013) Exp: Red colour of sun at the time of sunset is because of scattering of light.

Answer 175

(C) (SSC CHSL 2012) Exp: The light from the stars undergoes multiple refractions in atmosphere before reaching to our eyes. Therefore stars appear twinkling at night.

Answer 176

(D) (SSC CHSL 2011) Exp: The light rays coming from the bottom of tank comes to observer after undergoing refraction. The bent light appears to be coming from above the surface (than from actual surface). That is why tank appears shallower.

Answer 177

(A) (SSC CPO S.I 2017) Exp: The light gets refracted at the surface of water. Thus the light reaching the eye of an observer appears to be coming from above than the actual depth of swimming pool.

Answer 178

(C) [SSC CHSL 2015] Exp: Apparent depth = Real Depth Refractive index Refractive index for violet will be maximum, hence its apparent depth will be minimum. Hence, violet appears least raised. Lens and Mirror

Answer 179

(B) [SSC CGL Exam, - 2011] Exp: Flint glass is an optical glass which has relatively high refractive index. Flint glass contains 60% lead oxide.

Answer 180

(C) [FCI Asst. 2012] Exp: The nearest point at which an object can be brought into focus by an eye is called as near point. For a person having hypermetropia, the near point is greater than is 25 cm.

Answer 181

(A) (SSC LDC 2011) Exp: Concave mirrors form magnified image. Due to this, Concave mirrors are used in head mirror of ENT specialists.

Answer 182

(D) [SSC CGL 2016] Exp: Convex mirror form diminished image thus larger field is covered. Thus, we can easily see the large traffic behind.

Answer 183

(D) (SSC Const. (GD) 2013) Exp: Compound microscope is an optical instrument consisting of two convex lenses of short focal lengths. It is used to observe highly magnified image of very tiny objects.

Answer 184

(D) (SSC CHSL 2012) Exp: Convex mirror form diminished image, thus it provides larger view of traffic.

Answer 185

(B) (SSC Const. 2016) Exp: In myopia, image is formed in front of retina. So concave lens is used to correct myopia because it has diverging power thus it moves the image back to the retina.

Answer 186

(C) (SSC steno. 2011) Exp: A magnifying glass is a convex lens. It produces a magnified image of an object.

Answer 187

(B) (SSC CISF Const. 2011) Exp: A shaving mirror is a concave mirror it forms upright and enlarged image.

Answer 188

(B) (SSC Multitasking 2011) Exp: Headlight of vehicles have concave mirror and the bulb of the headlight is placed at the focus of the mirror. So that light rays spread out to infinity and a large distance ahead is visible.

Answer 189

(D) (SSC CPO 2015) Exp: Electron microscope has high magnification and resolution and it employs electron beams in place of light.

Answer 190

(D) (SSC Matric Level 2008) Exp: A periscope works on the laws of reflection. Two mirrors are placed at 45° to each other, light incident on one mirror is reflected and falls on the other mirror which is further reflected to reach human eye.

Answer 191

(B) (SSC Matric Level 2006) Exp: Silver is the best reflector of light. That is why silver is coated at the back surface of mirror.

Answer 192

(A) (SSC CHSL Tier-I 2016) Exp: 1 v - 1 u = 1 f 1 1 1 10 40 f 4 1 1 40 f f = 8 cm Power = 1 f inmetres = 100 8 = 12.5 Dioptre

Answer 193

(B) (SSC CHSL Tier-I 2016) Exp: 1 1 20 60 = 1 f 3 1 60 = 1 f f = 60 4 cm f = 60 4 10 P = 20 3 = 6.67 Dioptre

Answer 194

(C) Exp: 1 1 1 20 25 f 5 4 1 100 f f = 100 cm 9 f = 1 9 m Power = 1 f = 1 1/9 = 9 Dioptre

Answer 195

(D) (SSC Tax Ass. (Income Tax & Central Excise 2006) Exp: Prism is a transparent object. The triangular refracting surface of prism split the white light into its constituent components.

Answer 196

(D) (SSC CPO S.I 2008) Exp: Polaroids are used in 3D glasses to create the illusion of 3-Dimensional images.

Answer 197

(B) (SSC CGL Tier-I 2010) Exp: A concave lens always forms virtual and erect image because it is a diverging lens & rays do not actually meet each other after refraction.

Answer 198

(C) (SSC CPO (S.I, ASI & Intelligence offier) 2011) Exp: Telescopes has lenses of long focal length and microscopes has lenses of short focal length.

Answer 199

(C) [SSC FCI 2012] Exp: When the object is placed between the principal focus and the pole of concave mirror, the image formed will be magnified, virtual and erect.

Answer 200

(B) [SSC FCI 2012] Exp: Convex mirrors always produce images that are reduced in size, when body is placed at any place between infinity and pole of mirror.

Answer 201

(C) [SSC MTS 2013] Exp: Convex mirrors always produce smaller image and same size of image can be produced by plane mirror. So the nature of mirror will be convex and plane.

Answer 202

(B) [SSC CGL 2006] Exp: Zoom lens is a lens which allows a camera by changing a distant shot to a close-up by varying its focal length.

Answer 203

(A) [SSC CHSL 2013] Exp: Dioptre is the unit of power of lens. It is equal to the reciprocal of the focal length of lens.

Answer 204

(D) [SSC CHSL 2012] Exp: Radio telescopes are all weather, highly efficient and can work both during day and night. Hence, they provide a wider usability than optical telescope.

Answer 205

(A) [SSC CPO 2012] Exp: Polaroids are used to eliminate the glare by headlight in motorcars as they cut the horizontally polarised light which falls on it, there by reducing glare. Eye

Answer 206

(B) (31 January Evening) Exp: Sclera is the tough outer layer of the eye which protects the inner structures of eye.

Answer 207

(B) (SSC CGL 2016) Exp: A colour blind person cannot distinguish between Red and Green. Colour blind people are unable to fully 'see' red, green or blue light.

Answer 208

(B) (SSC CGL 2016) Exp: 25 cm is the least distance of distinct vision. Least distance of distinct vision is the minimum comfortable distance between the naked human eye and object.

Answer 209

(D) (SSC CGL 2016) Exp: In myopia a person cannot see distant object as the rays meet at the front of retina. Therefore distant object appear blurred.

Answer 210

(B) (SSC const. 2013) Exp: Under normal lightening conditions the cones of the eyes are most sensitive to green colour and then yellow colour.

Answer 211

(B) (SSC Steno. 2010) Exp: A person having myopia can see clear object only in the range of 8 cm to 50 cm.

Answer 212

(C) (SSC Steno. 2010) Exp: In human eye, lenses have the largest refractive index whereas largest refraction occurs at cornea due to change of medium from air to outer surface of cornea.

Answer 213

(D) (SSC Matric Level 2006) Exp: In hypermetropia image is formed behind the retina. It can be corrected using convex lens as convex lens has converging power. It converges light at the retina and a clear image is formed.

Answer 214

(C) (SSC MTS 2006) Exp: Simple microscope uses biconvex lens which forms enlarged, erect and virtual image of the object.

Answer 215

(B) Exp: During solar eclipse intensity of ultraviolet rays is increased which affects the retina of human eyes.

Answer 216

(B) (SSC CPO SI 2006) Exp: Short sightedness known as Myopia. In this image is formed in front of retina. So, concave lens is used to correct myopia because of its diverging power it moves image back to the retina.

Answer 217

(A) (SSC Combined Matric 2000) Exp: Myopia also known as short sightedness in which a person can see near object clearly but cannot see distant object distinctly.

Answer 218

(B) (Combined Matric Level 2002) Exp: Owls have more number of rods (which help to see at night) in their eyes and they have large eyes which makes more light to enter in the eyes.

Answer 219

(A) (SSC CHSL Tier-I 2016) Exp: Myopia is also known as Short sightedness in which a person can see near object clearly but cannot see distant object distinctly.

Answer 220

(D) [SSC CPO 2006] Exp: As in outer space there is no atmosphere to scatter light. So sky appears black to an astronaut.

Answer 221

(D) [SSC CGL 2006] Exp: Colour Blindness is the inability of human eye to distinguish between different colours. Colour blindness can not be corrected by any lens.

Answer 222

(D) [SSC CHSL 2013] Exp: Protanopia is a type of colour blindness in which a person cannot distinguish between Blue, Red and Green colour.

Answer 223

(B) [SSC LDC 2005] Exp: The colour of any object depends on the colour of the light source and wavelength of light reflected by that object. Miscellaneous

Answer 224

(A) (SSC constable (GD) 2013) Exp: Speed of light is 3×108 m/s. It is denoted by 'c'

Answer 225

(D) (SSC CGL 2013) Exp: Photon is the packet of energy. It is also known as quanta. Light wave consists of number of photons.

Answer 226

(D) (SSC CHSL 2010) Exp: Laser is a coherent, monochromatic unidirectional beam of light.

Answer 227

(D) [SSC CHSL 2013] Exp: Persistence of vision is the ability of an eye to see image of an object even after the object has been removed.

Answer 228

(C)Exp: Newton's disc is made by colouring seven colors on wedge of paper and pasting it on the rotating wheel. When the wheel is rotated, our eye is unable to see the colours seperately and sees the colours mixed together to form white. It is possible due to the principle of persistence of vision.

Answer 229

(A) (SSC CHSL 2010) Exp: Solar cell works on the principle of photovoltaic effect i.e. when light falls on some particular substance a voltage is created.

Answer 230

(B) (SSC constable 2012) Exp: Light year is the distance travelled by light in one year in space.

Answer 231

(B) (SSC CHSL 2011) Exp: Ozone layer consists of O3 molecules, it protects the earth atmosphere from harmful ultra-violet rays.

Answer 232

(C) [SSC CHSL 2011] Exp: Red, Blue and Green are primary colours which are used to produce other colour on intermixing.

Answer 233

(D) (SSC Steno 2011) Exp: In cathode ray tube images are produced when an electron beam strikes a phosphor-coated screen. Its basic components are electron gun, deflecting coils, phosphorcoated screen, shadow mask etc.

Answer 234

(D) (SSC CHSL Tier-I 2016) Exp: Light travels in vacuum with the speed of 3×108 m/s.

Answer 235

(C) (SSC CHSL Tier-I 2016) Exp: Gordon gould was the first one to publish his paper on LASER in 1959.

Answer 236

(A) (SSC CHSL Tier-I 2016) Exp: In 1962, Nick Holonyak, invented the first visible light LED.

Answer 237

(C) (SSC CHSL Tier-I 2016) Exp: Cyanometer is the instrument which is used to measure the intensity of blue colour of sky.

Answer 238

(A) [SSC CGL 2012] Exp: Lumen is the SI unit of luminous flux. Luminous flux is the measure of total quantity of visible light emitted by any source.

Answer 239

(D) [SSC FCI 2012] Exp: White light comprises seven constitutent components namely VIBGYOR (Violet, Indigo, Blue, Green, Yellow, Orange and Red.)

Answer 240

(B) [SSC CGL 2010] Exp: Atomic clock is regulated by the vibrations of atomic or molecular system such as caesium

Answer 241

(D) [SSC CHSL 2013] Exp: When a light of suitable wavelength falls on a metal surface it transfers its energy to that surface and an electron is ejected. This principle is called Photoelectric effect.

Answer 242

(B) [SSC CGL 2011] Exp: When sodium gets excited by energy, it gives out a yellowish light.

Answer 243

(A)Exp: Photo means light. Hence, photo-oxidation is the process in which oxidation is caused out by light.

Answer 244

(C) [SSC Steno. 2005] Exp: Hologram is a 3-d image formed by the interference of light beams from any coherent light source.

Answer 245

(B) [SSC CPO 2006] Exp: Narinder Kapany an Indian born U.S scientist invented optical fibre.

Answer 246

(D) [SSC MTS 2006] Exp: Optical fibres are used for long distance communication. It is based on the principle of TIR. Light travels inside an optical fibre with little or no attenuation.

Answer 247

(C) [SSC Sten. 2014] Exp: C.V. Raman won Nobel Prize for his experiment of scattering of light called Raman effect.

Answer 248

(C) [SSC MTS 2008] Exp: Light waves are electro-magnetic waves. They travel in the form of electric and magnetic field.

Answer 249

(C) [SSC MTS 2006] Exp: Sunlight takes 8.3 min to reach the surface of earth.

Answer 250

(C) [SSC CGL 2004] Exp: Speed of light does not depend on the temperature of medium. Speed of light is constant.

Answer 251

(C) [SSC CPO SI 2005] Exp: First real measurement of light was done by Ole Romer in 1676.

Answer 252

(A) [SSC Sec. Officer 2007] Exp: Complentary colours are those colours, which gives black or white colour when mixed with each other.

Answer 253

(A) (SSC CPO 2017) Exp: Resolving power is the capacity of an optical instrument to resolve two points which are closely placed.

Answer 254

(B) (SSC CPO 2017) Exp: Kaleidoscope is based on the principle of reflection. The law of reflection states that when a light hits a smooth and shiny surface at certain angle, the light is reflected away from that surface at the same angle.

Answer 255

(A) (SSC CPO 2017) Exp: A magnifying glass is a convex lens that is used to produce a magnified image of an object. A magnifying glass can be used to focus light.

Answer 256

(D) (SSC CPO 2017) Exp: When two mirrors are placed parallel to each other. It forms infinite images of any object.

Answer 257

(C) (SSC CPO 2017) Exp: A Prism is a transparent optical element with flat and polished surfaces that refract light. A dispersive prism can be used to split sunlight into seven colours.

Answer 258

(A) (SSC CPO 2017) Exp: Dentist and ENT doctors use concave mirrors in their treatment procedure to obtain a larger image than the original size of teeth, ear or skin etc.

Answer 259

(C) (SSC CPO 2017) Exp: Law of Reflection states that angle of Incidence is always equal to the angle of Reflection.

Answer 260

(C) (SSC CGL 2017) Exp: T.H. Maiman invented first working laser. He made the first laser operate on 16 may 1960 at Hughes Research Laboratory in California, by shining a high-power flash lamp on a ruby rod with silver coated surfaces. So, it is also called Ruby laser.

Answer 261

(A) (SSC CGL 2017) Exp: The regular reflection is the reflection of light ray when they falls on a smooth (uniform) and glistening surface so, the reflected ray of light move only in a fixed direction or in one direction.

Answer 262

(D) (SSC CGL 2017) Exp: Black board doesn't reflect any colour. It absorbs all the colours/light that falls on it. So, it appears as 'Black', which is actually the absence of colour.

Answer 263

(C) (SSC CGL 2017) Exp: Diffraction of light is phenomena which occur when light wave passes by a corner or through an opening or slit that is physically the approximate size of even smaller than that light's wavelength.

Answer 264

(D) (SSC CGL 2017) Exp: Mirage is an optical illusion such as the appearance of a sheet of water in a desert or in which distant objects are seen inverted. It is formed by refraction and total internal reflection.

Answer 265

(A) (SSC CGL 2017) Exp: Speed of light is maximum in vacuum because in vacuum, there is no particles present for the photons to interact with. So it doesn't get absorbed by any particle and appears to travel with the maximum speed.

Answer 266

(D) (SSC CGL 2017) Exp: A convex mirror is used as rear view mirror because they form erect, virtual and diminished images which allow the driver to view a large area of traffic.

Answer 267

(A) (SSC CGL 2017) Exp: A concave mirror forms enlarged image of the object. The nature of image depends on the distance of the object from the concave mirror.

Answer 268

(B) (SSC CGL 2017) Exp: The light rays coming from the bottom of tank comes to observer after undergoing refraction. The bent light appears to be coming from above the surface (than from actual surface). That is why tank appears shallower.

Answer 269

(B)Exp: The three primary colours in additive mixing are Red, Green and Blue. In the absence of colours or when no colour are showing, the result is black. If all three primary colours are showing the result is white. When Red and Green is combined, the result is Yellow.

Answer 270

(C) (SSC CGL 2017) Exp: Photoelectric effect/Photoemission shows the particle nature of light.

Answer 271

(A) (SSC CGL 2017) Exp: When blue colour and green colour are mixed, the result is cyan colour.

Answer 272

(D) (SSC CGL 2017) Exp: Optical fibre works on the principle of Total Internal Reflection. Light travels great distance without undergoing attenuation inside the fibre.

Answer 273

(A) (SSC CGL 2017) Exp: Refraction of light is defined as the bending of ray of light rarer to denser when it passes from rarer medium to denser medium and vice-versa is called refraction of light.

Answer 274

(A) (SSC CGL 2017) Exp: Side/rear-view mirror of a vechicle is a convex mirror as it gives diminished, virtual and an erect image of the side or rear with wider field of view of traffic.

Answer 275

(A) (SSC CGL 2017) Exp: The image formed by a plane mirror is always virtual (that cannot be obtained on a screen) and of the same shape and size as the object it is reflecting.

Answer 276

(C) (SSC CGL 2017) Exp: The impression of an image does not vanish immediately from the retina. It persists there for about 1 th 16 of a second. So, if still images of a moving object are flashed on the eye at a rate faster than 16 per second, then the eye perceives this objects as moving.

Answer 277

(B) (SSC CGL 2017) Exp: Concave mirror forms real and inverted image of an object.

Answer 278

(C) (SSC CGL 2017) Exp: The Law of Reflection states that the incident ray, the reflected ray and the normal to the surface of the mirror all lie in the same plane. Further more, the angle of incidence is equal to the angle of reflection.

Answer 279

(C) (SSC CGL 2017) Exp: The phenomenon due to which left-hand side of an object appears as right-hand side of the object and viceversa is called Lateral Inversion. For example, the word AMBULANCE is painted left-right inverted on the ambulance.

Answer 280

(B) (SSC CGL 2017) Exp: A spherical mirror is a mirror which has the shape of piece cut out of a spherical surface. There are two types of spherical mirror :- (A) Convex mirror (B) concave mirror.

Answer 281

(B) (SSC CGL 2017) Exp: The angle formed between the normal and the incident ray at the point of incidence is called the Angle of Incidence.

Answer 282

(C) [SSC CGL 2015] Exp: The speed of sound in a medium is inversely proportional to the square root of medium's density. Density of moist air is less than density of dry air. Hence, speed of sound is more in moist air as compared to dry air.

Answer 283

(A) [SSC CPO 2015] Exp: Hertz is the unit of frequency. It is equal to one complete cycle per second.

Answer 284

(A) Exp: Noise pollution is measured in Decibels.

Answer 285

(D) Exp: Decibel is the unit used to measure the intensity of sound.

Answer 286

(B) Exp: Permissible noise level at residential area during day time is 55 dB and night time is 45 Db.

Answer 287

(A) Exp: The term 'Ultrasonic' refers to anything above the frequencies of audible sound and includes waves of frequency greater than 20 KHz.

Answer 288

(D) [SSC MTS 2013] Exp: Audible range of frequencies, that human ear can sense is 20-20,000 Hz. But it is more sensitive to sounds between 1,000 Hz and 4,000 Hz.

Answer 289

(B) [SSC CHSL 2015] Exp: Intensity of wave is directly proportional to square of its amplitude 1 2 I I = 25 9 I A2 1 2 I I = 2 1 2 2 A A 25 9 = 2 1 2 2 A A 1 2 A A = 25 9 = 5 3 A1: A2 = 5: 3

Answer 290

(C) [SSC CGL 2012] Exp: Sonic boom is the common name of loud noise created by the shock wave produced by supersonic air plane. It is a conical cavity of disturbance behind the tail of supersonic air plane.

Answer 291

(A) [SSC MTS 2014] Exp: Velocity of the sound wave depends upon temperature, density of medium in which it is travelling. It also depends on moisture content in medium.

Answer 292

(D) [SSC CGL 2008] Exp: Sound wave requires medium to travel. So it cannot pass through vaccum.

Answer 293

(A) Exp: Sound wave travels fastest in solids as the atoms are tightly bounded and elastic content is higher. Speed of the sound is directly proportional to the square root of elastic property of medium.

Answer 294

(B) [SSC Sten. 2014] Exp: Same as above 14. Pitch of a sound depends upon its - (A) Frequency (B) Intensity (C) Velocity (D) Amplitude (A) [SSC Sten. 2011] Exp: Pitch of the sound depends upon frequency of the sound. Frequency is measured in Hertz and it is equal to one vibration per second.

Answer 295

(A) [SSC CHSL 2015] Exp: On increasing the temperature kinetic energy of air molecules increases. So, number of vibrations per second increases. Hence, there is an increase in frequency with an increase in temperature.

Answer 296

(D) [SSC CGL 2011] Exp: Echolocation is the use of sound waves to locate where the objects are in space. Echolocation is used by mammals like dolphins, bats and whales.

Answer 297

(C) [SSC FCI 2012] Exp: Forced vibrations are the vibration induced in body under the influence of another vibrating body. Table top experiences forced vibrations due to tuning fork. As more air molecules are in contact with table top it induces vibrations among them and hence a louder sound is heard.

Answer 298

(D) Exp: Sound waves are longitudinal waves and polarisation can take place only in transverse waves.

Answer 299

(B) Exp: Same as above

Answer 300

(B) Exp: Velocity of sound depends on elastic property of material medium and density of material medium. v = B ρ B = Bulk modulus ρ = density of medium

Answer 301

(B) Exp: The overtones present in the sound gives us knowledge of the source as every source has fixed fundamental frequency. When instruments are played above fundamental frequency overtones can be recognized.

Answer 302

(D) Exp: All the three except sound waves are Transversal, whereas sound waves are Longitudinal.

Answer 303

(A) Exp: Waveform of the sound wave pertains to quality of the sound. Every instrument has a different waveform.

Answer 304

(A)Exp: Beat is an interference pattern between two sounds of slightly different frequencies.

Answer 305

(C) Exp: Loudness of sound is a measure of response of sound to our ear. It depends upon the amplitude of sound wave.

Answer 306

(A) Exp: Pitch of the sound depends upon frequency of the sound wave. The higher the frequency, the higher the pitch will be.

Answer 307

(D) Exp: Quality of sound depends on the waveform and quality of musical note depends on overtones.

Answer 308

(A) Exp: Infrasonic waves have greater wavelength than that of audible sound. Infrasonic sound is very low frequency sound.

Answer 309

(B) Exp: Frequency of the sound does not change with the change in medium.

Answer 310

(C) Exp: Kundt's tube consists a long transparent horizontal pipe which contains a fine powder such as talc.

Answer 311

(D) [SSC CGL 2014] Exp: Ultrasonic sounds with frequency more than 20KHz are used in the sonography which is used to diagnose internal body org

Answer 312

(A) Exp: Echo is produced due to reflection of sound waves through a large obstacle.

Answer 313

(A) Exp: SONAR locate object from the echo of a signal that is reflected off the object.

Answer 314

(B) [SSC CGL 2013] Exp: Sonometer is used to study the behaviour of a vibrating string. It works on the principle of resonance.

Answer 315

(A) Exp: Same as Q.No. 12

Answer 316

(A) Exp: Speed of sound in gas is proportional to square root of isothermal elasticity. Why isothermal-because change in temperature will bring change in speed of sound.

Answer 317

(D) Exp: Doppler's effect can be described as change in frequency or wavelength of a wave for an observer which is moving with respect to its source.

Answer 318

(D) (SSC Tax Asst. (Income Tax & Central Excise 2006) Exp: Bats can hear higher frequencies of sound beyond the range of human hearing and ultrasonic sound higher frequency sound. That is why bats can hear ultrasonic sound.

Answer 319

(B) (SSC Tax Asst. (Income Tax & Central Excise 2006) Exp: Sonar (Sound, Navigation and Ranging) is used to navigate, communicate with or detect objects on or under the surface of water.

Answer 320

(B)Exp: Velocity of the sound waves depends upon temperature, density of medium in which it is travelling through and also depends on moisture content in medium but it does not depend on pressure of the medium.

Answer 321

(B) (SSC CPO S.I 2010) Exp: Ultrasonic waves are those waves whose frequency is above 20 KHz. It is inaudible to human ear.

Answer 322

(D) (SSC CPO S.I 2010) Exp: The velocity of sound increases with increase in temperature of medium or vice versa as V T

Answer 323

(C) (SSC Combined Matric Level (Pre) 1999) Exp: Microphone converts one form of energy to another form of energy. Microphone converts sound energy into electrical energy.

Answer 324

(B) (SSC (10+(B) Level D.T.O & LDC 201(B) Exp: 0.0002 bar is the least pressure created by sound waves to which human ear is sensitive.

Answer 325

(B) (SSC Graduate Level Tier-I 201(C) Exp: Tolerance limit of ears refers to the limit upto which human ears are sensitive without getting any damage. This limit is 60 dB for ordinary and 80 dB as extreme limit.

Answer 326

(B) (SSC CGL Tier-I 2015) Exp: Velocity of sound depends on density of medium. In rainy days air will be more moist and density will be lower, sound will travel faster.

Answer 327

(A) (SSC CHSL (10+(B) LDC, DEO & PA/SA 2015) Exp: As the temperature rises, molecules begin to vibrate more rapidly, thereby increasing the frequency of sound.

Answer 328

(C) (SSC sec. officer 200(A) Exp: Sound of higher pitch will be heard compared to the sound of lower pitch.

Answer 329

(C) (SSC CHSL Tier-I CBE) 2016) Exp: Candela is the SI unit of Luminous intensity. Hertz, Decibel and Mach all are associated with sound wave.

Answer 330

(D) (SSC CHSL (10+(B) LDC, DEO & PA/SA 2015) Exp: v 1 ρ 1 2 v v = 1 ρ oxygen hydrogen v v = hydrogen oxygen ρ ρ = 1 16 oxygen nydrogen v v = 1 4 = 1: 4

Answer 331

(C) (SSC (10+(B) Level D.E.O & LDC) 201(B) Exp: As microphone is a type of transducer, it converts sound energy into electrical energy.

Answer 332

(D) (SSC CGL (CBE) 2016) Exp: We cannot hear the sound of explosion which happend on moon because sound needs medium to travel and moon is surrounded by vacuum.

Answer 333

(B) (SSC Combined Matric Level 200(B) Exp: Bats use ultrasonic sound waves to locate the objects in space.

Answer 334

(C) (SSC CGL Tier-I 2016) Exp: Quality of musical note depends on overtones of sound. Overtones of sound also referred as harmonics.

Answer 335

(A) Exp: Percieved loudness of sound is measured in decibel (dB).

Answer 336

(A) Exp: Hydroscope - It is used for seeing below the surface of water. Hydrophone - It is used to detect sound waves under water.

Answer 337

(A) (SSC CHSL Tier-I 2016) Exp: The SI unit of intensity of sound is watt per square meter. It is commonly referred to as decibles (dB).

Answer 338

(B) (SSC CHSL Tier-I 2016) Exp: Shrillness of sound depends on its frequency. Voice is shrill because of higher frequency of sound.

Answer 339

(B) (SSC CPO 2017) Exp: Sonometer is used to study the laws of vibrating strings. It is a device based on the principle of Resonance. It is used to verify the laws of vibration of stretched string and also used to determine the frequency of a tuning fork.

Answer 340

(C) (SSC CPO 2017) Exp: In fluid mechanics, Mach number is defined as the ratio of the speed of a body to the speed of sound in the surrounding medium. It is used with a numeral (as mach 1, mach 2, etc.) to indicate the speed of sound, twice the speed of sound and so on.

Answer 341

(C) (SSC CPO 2017) Exp: The S.I. Unit of frequency is hertz. 1 Hertz (Hz) is defined as one Cycle per second. It is named after Heinrich Rudolf Hertz.

Answer 342

(A) (SSC CPO 2017) Exp: Infrasonic sound is a sound that is lower in frequency than 20 Hz or cycles per seconds. The lower limit of human hearing.

Answer 343

(C) (SSC CGL 2017) Exp: The minimum distance to hear an echo will be partly based upon the observers ability to resolve different sounds. Considering the speed of sound to be 343 m/s, the minimum distance (d = vt) to hear distinct echo is 17.2 m.

Answer 344

(B) (SSC CGL 2017) Exp: Pitch is determined by the frequency of a wave and frequency is the combination of wavelength and speed at which the wave is travelling.

Answer 345

(D) (SSC CGL 2017) Exp: S.I. Unit of frequency is hertz (Hz). It is equal to one complete cycle per second.

Answer 346

(B) (SSC CGL 2017) Exp: Ian Donald (1910-87) was a Scottish physician who pioneered the use of diagnostic ultrasound in medicine.

Answer 347

(A) (SSC CGL 2017) Exp: The S.I. unit of intensity of sound is Decibel.

Answer 348

(C) (SSC CGL - 2008) Exp: When a person on a freely rotating turn-table spreads his hands outward, it will decrease the angular rotation, maintaining the same angular momentum.

Answer 349

(D) (SSC Sten. 2011) Exp: As momentum is proportional to mass of any object, the moment of heaviest object will be the maximum.

Answer 350

(C) (SSC MTS 2002, COP 2010) Exp: According to Law of Conservation of Momentum, total momentum of an object before explosion is equal to the momentum of the object after explosion.

Answer 351

(B) [SSC Section officer (Audit) 1997] Exp: Force = mass × acceleration = m × dv dt If speed of car will be doubled then force required to stop the car will be doubled.

Answer 352

(B) (SSC Section officer (Audit) 1997) Exp: Impulse = Force Time = Kg m/sec2 sec = kg m/sec MLT-1 momentum = m v = kg m /sec MLT-1 Impulse and momentum both have same dimensions.

Answer 353

(A) (SSC Section officer (Audit) 1997) Exp: When rain drops fall from great height, they fall due to gravitational pull and their velocity depends on their size.

Answer 354

(B) (SSC Section officer (Audit) 2003) Exp: When a player catches a ball, he lowers his hand to lower the rate of change of momentum.

Answer 355

(C) (SSC Tax ass. InT. 2004) Exp: Equation y = mt + c represents linear velocity with respect to time linear velocity and time graph shows that particle is moving with constant acceleration.

Answer 356

(C) (SSC Section officer (Audit) 2008) Exp: The swing of a spinning cricket ball in air can be explained on the basis of turbulence caused by wind

Answer 357

(A) (SSC Exm. 2010) Exp: The spokes used in the wheel of bicycle increases its moment of inertia. The more is the moment of inertia, the more smooth will be the motion of bicycle

Answer 358

(B) (SSC combined Graduate - 2011) Exp: The main function of ball bearings is to reduce friction between the surface of bearing and the surface it is rolling over.

Answer 359

(B) (SSC Combined Matric Level- PRE 2000) Exp: The velocity of sphere depends on the height of inclined plane and acceleration due to gravity.

Answer 360

(A) (SSC combined Matric Level 2002) Exp: An athlete runs before the long jump to gain the moment of inertia to get forward momemtum in order to get longer jump.

Answer 361

(C) (SSC combined Martirc Level- 2002) Exp: According to Newton's First Law of Motion an object will stay at rest if in rest and stays in motion if in motion unless an external force is applied on it so to hit the target pilot should release the bomb before the target, because bomb will have the velocity of plane.

Answer 362

(A) (SSC Combined Martirc Level- 2006) Exp: According to Law of Conservation of Momentum, total momentum of objects before collision is equal to the total momentum of the objects after collision. It will also apply in case of explosion. That is why the total momentum of all fragments of bomb after explosion will be zero.

Answer 363

(A) (SSC Combined Martirc Level- 2006) Exp: Slope of velocity-time graph represents acceleration.

Answer 364

(C) (SSC Sten. Grade - 2011) Exp: Railway tracks are banked on curves so that it provides necessary centripetal force to enable it to move smoothly round the curve

Answer 365

(C) (SSC 10+2 Level Data Entry- 2012) Exp: When a running car stops suddenly, the passengers tend to lean forward due to inertia of motion.

Answer 366

(A) (SSC CHSL, LDC - 2014) Exp: The rubber ball suffers greater change in momentum than metal ball that is why rubber ball rebounds and metal ball does not rebound.

Answer 367

(C) (SSC CGL- 2014) Exp: The motion of wheels of bullock cart is an example of both translatory and rotatory motion.

Answer 368

(B) (SSC CGL- 2014) Exp: Moment of Inertia is the property of mass of a body. It does not depend upon its angular velocity.

Answer 369

(B) (SSC CGL- 2014) Exp: Torque = Force × distance To open a door easily, handle should be fixed at greatest distance to give maximum torque to open the door.

Answer 370

(D) (SSC CGL - 2014) Exp: If a particle is moving in a uniform circular motion with constant speed v along a circle of radius r, then the acceleration of particle will be 2 v r .

Answer 371

(D) (SSC CHSL (10+2) DEO LDC 2014) Exp: Distance is directly proportional to the square of time Let distance = S time = t S t2 S = kt2 ds 2kt dt v = 2kt dv = 2k dt Hence, acceleration is constant

Answer 372

(A) (SSC CHSL (10+2) DEO & LDC 2014) Exp: Acceleration is defined as the rate of change of velocity. If an object is moving with constant speed, it cannot be accelerated.

op phys 1 Flashcards

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