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gcse phys > waves > Flashcards

waves Flashcards

(72 cards)

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1
Q

what are transverse waves with example

A

when oscillations are perpendicular to the direction of energy transfer (direction of the wave)
ripples on water

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2
Q

what are longitudinal waves with example

A

oscillations are parallel to direction of energy transfer, must travel in a medium (state)
sound waves travelling through air

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3
Q

what do you call the vibrations of waves

A

oscillations

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4
Q

what do you call it when the regions where air particles are close together vs when air particles are spaced out

A

compressions
rarefactions

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5
Q

what do particles transfer in a wave

A

energy, NOT the particles themselves

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6
Q

what is amplitude

A

maximum displacement of a point on a wave from its undisturbed position (middle line)

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7
Q

what is wavelength and how is it measured

A

distance between the equivalent points on two adjacent waves

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8
Q

what is wavelength and how is it measured

A

distance between the equivalent points on two adjacent waves

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9
Q

what is frequency and what is it measured in

A

number of complete waves passing a point per second
hertz (1Hz = 1 wave per second)

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10
Q

what is the period of a wave

A

time (s) for a complete wave to pass a point

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11
Q

what is wave speed

A

speed (m/s) that energy is transferred

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12
Q

how to measure speed of sound waves

A

• B stand set distance from 15 random students, further the better as longer distance = longer time, meaning easier to start and stop timers
• students start timer when B clashes cymbals, stop the timer when they hear it
• calculate speed (distance/time taken) then find mean

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13
Q

how to measure speed of water ripples

A

• place a piece of paper with a ruler alongside below a ripple tank and a lamp above
• turn on lamp and dipper of the tank
• take a photo of shadows and ruler and measure distance of 10 wavelengths, then divide by 10 to get 1 wavelength (in m)
• place timer next to paper and mark a point on paper
• count waves passing a point in 10 seconds, divide by 10 to find 1 second. if too fast, record and slow down

wavelength x frequency = speed :)

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14
Q

how to measure speed of waves in solid

A
  • connect a signal generator to a vibration generator
  • attach string to vibration generator, loop around a pulley and hang a mass on other end to keep string taut
  • turn on power and adjust frequency on signal generator until there are clear wavelengths
  • measure all half-wavelengths, divide by number of half-wavelengths, then times by 2 to get 1 wavelength
  • calculate wave speed
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15
Q

what can happen when a wave hits a boundary of a different material

A

depending on wavlength and material:

• absorbed: energy transfers to material’s energy stores
• transmitted: travels through & often refracts
• reflected

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16
Q

how do draw ray diagram for reflection

A

• draw ray striking surface (incident ray) with arrow
• draw dotted line perpendicular to surface (the normal)
• measure angle (angle of incidence)
• angle of reflection = angl of incidence
• draw ray leaving surface (reflected ray) with arrow

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17
Q

specular vs diffuse rays

A

spec: single direction, smooth surface
diff: scattered, rough surface, matte

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18
Q

how to investigate reflection by different surfaces and refraction by different substances

A

• draw straight line down centre of a3
• draw the normal using protractor
• place glass block against first line, normal at the centre
• draw around block
• turn off lights and direct ray box at the normal
• mark the incident & reflected ray and the ray leaving block, known as the transmitted ray, with crosses
• remove block and use ruler to draw rays. connect normal to transmitted ray to show path
• use protractor to find angle of incidence/reflection and angle of refraction (normal ray & path)
• repeat with range of material e.g plastics

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19
Q

results of reflection & refraction light practical

A
  • angle of incidence = angl of reflection for all objects
    • not dependent on material
  • angle of refraction - different for all objects
    • dependent on density of material
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20
Q

how does sound travel

A

vibration of source, causes air to move in a series of compressions and rarefactions. this is a sound wave (longitudinal)
vibrations can pass through mediums

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21
Q

how do we hear and to what extent

A

sound waves hit ear drum, a thin membrane, causing it and other parts of inner ear to vibrate and create electrical signals that allow the sensation of sound

20 - 20 000 Hz as other frequencies may not cause eardrum to vibrate

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22
Q

speed of sound in different states

A

fastest in solids as vibrations pass easier through closer particles

slowest in gas

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23
Q

what is reflection and refraction of sound waves

A

reflection: echos
refraction: waves refract in different mediums, so wave speed changes as ws = wl x hz

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24
Q

how does the wave on cathode ray oscilloscope change with pitch and how does it change with volume

A

high pitch: high frequncy (more waves)
low pitch: smaller frequency

quiet: smaller amplitude
loud: bigger amplitude

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25
what is ultrasound
sound with frequency higher than 20 000 Hz
26
how can you measure how far away something is from a boundary using ultrasound
when wave hits a boundary it partially reflects use a detector to detect time taken for pulse to leave and reflect back
27
how is ultrasound used medically
to get images of foetus or internal organs e.g kidney boundaries between two organs will produce reflection
28
how are ultrasounds used industrially
to find flaws in pipes e.g a crack will cause earlier reflection
29
how do scientists know interior of earth
worked out where layers of different properties are by observing how seismic waves are absorbed and reflected
30
what are the different seismic waves
p waves: longitudinal, travel through solid and liquid. faster s waves: transverse, travel through solids
31
what do seismometers show about s waves and the earths structure
waves are not detected on other half of earth (shadow zone) means outer core is liquid as s waves cannot pass through
32
what do seismometers show about p waves and earths structure
waves are not detected in certain areas (shadow zones) as they refract as density changes shows outer core is liquid as p waves travel faster in solids than liquids
33
what are electromagnetic waves and some properties
transverse waves that transfer energy from a source to an absorber - do not need a medium to travel (can travel in space) and travel at same speed - absorbed, transmitted, or reflected depending on wavelength, e.g microwaves absorbed by food, reflected by metals
34
how do waves change through light spectrum
red - lower freq & longer wavelength | | | violet - higher freq & shorter wavlength
35
how to remember spectrum for all electromagnetic waves
Raw Meat Is Very Unsanitary eXept Giraffe
36
what is the order of the continuous electromagnetic spectrum and how do the waves change
Radio waves - low freq, long w/length Microwaves Infrared Visible light Ultraviolet X rays Gamma rays - high freq, short w/length
37
uses of radio waves and reason why
transmit radio signals and terrestrial tv signals - travel long distances before absorbed - diffract around hills - reflect off ionosphere so travel far
38
uses of microwaves and reasons why
heating food - energy absorbed from microwaves by water molecules in food causes temp increases communicate with space satellites - pass through atmosphere without being reflected or refracted
39
uses of infrared and reasons
heaters and cooking in oven - energy easily absorbed by surfaces monitor heat loss (infrared cameras) as hotter objects emit more IR
40
uses of visible light and reason
communication using fibre optics (thin strands of glass) light pulses are transmitted down fibres to carry information e.g tv signals - short w/length so carries lots of info
41
uses of ultraviolet and reason
energy efficient light bulbs. bulb surface absorbs uv energy and converts to visible light. requires less energy than normal lightbulb - short w/length so carries more energy than visible light tanning beds however causes ageing and cancer risks in skin
42
uses if x rays and gamma rays and reasons
medical images - broken bones/cancer - very penetrative so absorbed by tissue e.g bones
43
how to measure how much infrared is emitted by different surfaces
• fill leslie cube with hot water • point infrared detector at each of 4 surfaces and record amount of IR emitted. ensure distance is fixed
44
what is a leslie cube
metal cube with 4 different surfaces: shiny metallic, white, shiny black, matt black shows IR emission
45
result of infrared emission practical
emits least IR - shiny metallic - white - shiny black - matt black emits most IR
46
how to measure absorbance of infrared by different surfaces
• place two metal plates, one painted shiny metallic and one matt black, either side of infrared heater • on other side of plates, attach drawing pins at fixed distances up plate using vaseline • switch on heater and start timer • stop timer when vaseline melts and pins fall
47
results of absorbance of surfaces of IR
infrared absorbed transfers to thermal energy stores, melting vaseline. matt black surface absorbs faster
48
what is refraction
the changing of direction of waves when they move from one medium to another, as speed changes
49
what happens to waves travelling along the normal vs at an angle to a glass block
along: slower, same direction angle: ray slows, causing direction to bend towards normal. ray speeds up once left block, bends back away from normal
50
what is a wavefront diagram and what does it look like for light refracting through glass box
shows imaginary line connecting the same point in a set of waves (straight lines perpendicular to how the waves would be)
51
how do atoms change to generate em waves?
when atoms heated, electrons move to a higher energy level generates an em wave when it returns
52
how does nuclei change to generate em waves
gamma rays are emitted from nucleus of radioactive atoms, nucleus has less energy
53
properties of em waves
- cause changes to atoms (electrons, nuclei) when emitted/absorbed - emitted/absorbed over wide frequency range, the continuous spectrum
54
how is uv radiation dangerous
increase risk of skin cancer and cause premature aging of skin
55
how are x rays and gamma rays dangerous
ionising radiation - knock electrons off atoms when absorbed, causing mutations, increasing risk of cancer
56
what measures risk of damage from radiation
type and dose
57
how are radio waves produced
- electrons oscillate in the transmitter, producing radio waves - radio waves absorbed, causing electrons in receiver to oscillate - creates AC in receiver with same frequency as the radio waves
58
shape of convex lenses and symbol
thicker at centre vertical, double sided arrow
59
what happens to parallel rays of light passing through convex lens
rays converge to principal focus - centre of lens - axis - point rays meet - principal focus - distance of lens to focus - focal length
60
how to construct ray diagram for convex lenses
• draw line from top of object (marked on graph) through centre of convex lens (origin of graph) • draw line from top of object to lens (y axis), parallel to principal axis (x axis) • line at lens refracts. draw refracted ray passing through principal focus (marked F on x axis) • mark the top of the image (where rays meet) and connect perpendicular to x axis
61
image on ray diagram for convex lenses when object is - 2+ focal lengths from lens - 1-2 focal lengths from lens - <1 focal length from lens
- smaller, inverted, real - larger, inverted, real - larger, same way up, virtual
62
real vs virtual
real: rays meet at a point virtual: rays only appear to meet, could not be seen on a screen e.g a magnifying glass
63
shape of concave lens and symbol
thicker at edges vertical inverted arrow
64
what happens to parallel rays of light when passing through concave lens
rays diverge principal focus is behind lens, where diverging rays would meet.
65
how to draw ray diagram for concave lens
• draw line from top of object (marked on graph) through centre of convex lens (origin of graph) • draw line from top of object to lens (y axis), parallel to principal axis (x axis) • line at lens refracts. draw refracted ray passing through principal focus (marked F on x axis, it is before y axis unlike convex) • when lines meet shows image
66
image on ray diagram for concave lenses
- smaller, upright, virtual
67
how do colour filters react to light spectrum (colour wheel)
transmitting specific wavelengths and absorbing others
68
how do transparent/translucent objects react to light spectrum
transparent: transmit light so we see through translucent: scatters light we dont see through clearly
69
how do opaque objects react to light spectrum
white: all wavelengths reflect black: all wavelengths absorb coloured: all wavelengths absorbed, specific colour reflected
70
how does an objects temperature affect radiation
hot = short wavelength, high intensity
71
what is a perfect black body
object that absorbs of the radiation incident on it, none reflected or transmitted good absorption = good emission
72
how does radiation affect earths temperature
- sun emits short wavelength radiation e.g uv, visible light - some reflected by clouds - rest absorbed by surface, increasing temperature of earth - earth now emits IR back to space however: some is trapped by greenhouse gas some is reflected back to earth by clouds

gcse phys (4 decks)

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