Unit 2: Waves and Radiation Flashcards Preview

National 5: Physics > Unit 2: Waves and Radiation > Flashcards

Flashcards in Unit 2: Waves and Radiation Deck (88):
1

What is a Wave?

Something that transfers energy from one point to another

2

Transverse Wave

Particles of the medium vibrate at right angles to the direction the energy travels.

Examples: E-M Waves + Water Waves

3

Longitudinal Waves

Energy travels along in the same direction as the particles vibrate.

Example: Sound Waves

4

Wavelength

DIstance from a point to the point the wave begins to repeat itself. Could be from peak to peak or trough to trough. Measured in metres(m) and has the symbol λ

5

Frequency

Number of waves produced in 1 second by the source producing the wave. Measured in Hertz(Hz) and has the symbol f

6

Amplitude 

Half the distance from peak to trough or the height of the wave from rest position. Measured in metres(m)

7

Wave Speed

How quickly the wave travels from its source. Is value is the same as distance travelled in one second. Measured in metres per second(ms-1) and has the symbol v

8

Period

Time taken for one complete wave to be produced. Also time taken for one whole wave to pass a point. Measured in seconds(s) and has the symbol T

9

Speed of Sound in Air

340 ms-1

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Speed of Light in Air

3x108 ms-1

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Diffraction

The spreading out of waves when they go through a gap or past the edge of a barrier

The greater the wavelength, the greater the diffraction

12

Electromagnetic Spectrum

Consists of a group of radiations that all travel at the speed of light

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Visible Spectrum

Consists of a range of different colours of light that the human eye can detect. ROYGBIV

14

Radio Waves

At one end of the E-M spectrum. Greatest Wavelength. Lowest Frequency.

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Gamma Ray

At one end of the E-M spectrum. Shortest Wavelength. Greatest Frequency.

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Radio Waves Source

Electronic Circuits

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Radio Waves Detector

Aerial

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Radio Waves Typical Uses

Communications, Radio, TV

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Microwaves Source

Electronic Circuits

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Microwaves Detector

Aerial

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Microwaves Typical Uses

Communications Satellites

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Infrared Sources

Electronic Devices

Warm Objects, Sun

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Infrared Detectors

Electronic Detectors

Heat-Sensitive Papers

Black-Bulb Thermometer

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Infrared Uses

Remote Controls

Detector in Security Lighting

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Visible Light Sources

Sun

Electronic Devices

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Visible Light Detectors

Eyes

Photographic Film

LDR

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Visible Light Typical Uses

Seeing

Photography

Communication (Optical Fibres)

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Ultraviolet Sources

Sun

Gas Discharge

Lamps

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Ultraviolet Detector

Film

Causes Fluoresence in Some Objects (Money)

30

Ultraviolet Uses

Sun-Tan Lamp

Making Ions

Killing Bacteria

Making Vitamin D

31

X-Rays Sources

Very Fast Electrons Hitting a Metal Target

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X-Rays Detector

Photographic Film

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X-Rays Uses

Imaging Defects in Bones

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Gamma Rays Sources

Radioactive Nuclei Decaying

35

Gamma Rays Detectors

Photographic FIlm

G-M Tube

36

Gamma Rays Uses

Killing Cancerous Cells

Sterilisation of Surgical Equipment

37

Refraction

The changing of speed (and often direction) of a light ray or a wave when it moves from one medium to another

38

Normal

Imaginary line perpendicular to the substance the ligh is entering

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Angle of Incidence

Angle at which light hits the new medium. Taken from Normal to Incident Ray

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Angle of Refraction

Angle at whcih light rravels in new medium. Taken from Normal to Refracted Ray

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Convex Lens

Curves Outwards

Converges (Focuses) Light

Positive Power and Focal Length

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Concave Lens

Curves Inwards

Diverges (Spreads out) Light

Negative Power and Focal Length

43

Retina

Light Sensitive Cells on the back of the eye. Light should converge at this point for a clear image

44

Long-Sightedness

Eye Lens Not Powerful enough

Corrected using a Convex Lens

Able to focus on distant objects but not close objects

45

Short-Sightedness

Eye Lens Too Powerful

Corrected using Concave Lens

46

Ray Diagram Object > 2F

Image is:

  • Real
  • Inverted
  • Diminished

47

Ray Diagram Object at 2F

Image is:

  • Real
  • Inverted
  • Same Size

48

Ray DIagram Object < 2F

Image is:

  • Real
  • Inverted
  • Magnified

49

Ray Diagram Object

Image is:

  • Virtual
  • Right Way Up
  • Magnified

50

Critical Angle

When the angle of incidence reaches this the angle of refraction=90º

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Total Internal Reflection

When the angle of incidence is greater than the critical angle and the light is reflected back into the medium. (No Light Refracted)

52

Fibre Optic

Used to transmit light signals through a series of Total Internal Reflections

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Fibre Optic Advantages

Very Little Energy Lost

Huge signal Capacity - can carry many TV Channels/Telephone Lines

Secure - No signal escapes out of the edges

Cheaper,Lighter and more Flexible than copper wires

54

Fiber Scope (Endoscope)

Allows doctor to see inside patient using bundles of fibre optics

55

Alpha Particles (α)

Made of 2 protons and 2 neutrons (identical to helium nucleus). Heavy and Positively charged

56

Beta Particle (β)

 

Made of 1 very fast moving electron. Light and negatively charged

57

Gamma Ray (γ)

Part of the E-M spectrum. Has no mass, travels at the speed of light and has a very high frequency so a very high energy

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Other types of Nuclear Radiation

X-Rays, Fast and Slow moving Neutrons

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Ionisation

When an atom loses or gains an electron giving it a charge

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Ionising Radiation

Heavier Radidation is more ionising. Alpha most. Gamma least

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Alpha Penetration

Stopped by a few cm of air or a thin sheet of paper

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Beta Penetration

Stopped by a thin sheet of aluminium

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Gamma Penetration

Stopped by Lead or Concrete

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Ways of Detecting Nuclear Radiation

Geiger-Müller Tube

Film Badge

Scintillation Counter

Cloud Chamber

65

Geiger-Müller (GM) Tube

Tube has a high voltage applied to central rod. Low pressure gas is sealed inside. 
When radiation enters it ionises an atom of the low pressure gas, causing a current to flow

More radiation means a larger current

Doesn't distinguish between types of radiation

66

Film Badge

Badge has photographic film sealed in a lightproof plastic envelope.

Badge has different windows that allow different types of radiation through.

When radiation enters through the window it ionises the photographic film causing it to fog

67

Sources of Radiation

40% Radon Gas from Ground

18% Artificial Sources

15% Rocks

15% Human Body + Food

12% Cosmic Rays

68

Uses of Nuclear Radiation

Smoke Alarms

Carbon Dating

Paper Thickness Measuring

Detecting Leaking Pipes

Sterilising Hospital Equipment

Radiotherapy

69

Smoke Alarms

Alpha Particles ionise the air causing a small current to flow. When smoke enters it absorbs the alpha particles causing the curent to reduce and the alarm to sound

70

Paper Mills

Paper Thickness measured by how much beta radiation passes through the paper. 

71

Radiotherapy

Gamma Rays used to kill cancer cells

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Radiation Safety Rules

Keep time of exposure to a minimum

Hold radioactive sources using tongs

Wear protective clothing

73

Absorbed Dose 

Energy absorbed per kilogram. Measured in Greys(Gy) and has the symbol D

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Dose Equivalent

Takes into Account the radiation expoesed to. Measured in Sieverts(Sv) and has the symbol H

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Safe Radiation Dose

5mSv for general public

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Activity 

Number of nuclei that decay every second. Measured in Bequerels(Bq) and has the symbol A

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Half-Life

Time taken for the activity of a source to halve

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Fission

When a large nucleus (such as uranium) splits into two smaller nuclei plus a few neutrons. Energy released very large (E=mc2)

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Nuclear Power Stations

Use nuclear fission to produce huge amounts of energy. Fission occurs in uranium fuel rods

80

Moderator

Slows down neutrons so they can go on to cause further reactions

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Nuclear Power Advantages

Huge amount of energy produced from a small amount of fuel

Reaction produces no pollution

Running costs are small compared to running costs of a coal fired power station

Fraction of waste produced compared to coal

82

Nuclear Power Disadvantages

Waste is highly reactive with a long half life

Massive start up costs. Expensive to decomission

Risk of nuclear accients that could release huge amounts of radioactive material intp environment. (Fukashima,Chernobyl)

83

Fusion

When two small nuclei join together to form a larger one, releasing a huge amount of energy

84

Fusion Advantages

Huge amount of energy produced using a small amount of fuel

A fraction of waste is produced compared to the waste from coal

Waste is helium - a harmless gas

85

Fusion Disadvantages

Only happens at very high temperatures

Containing fuel at high temperatures isn't possible with current technology

More research needs to be done

86

If angle of incidence < critical angle

The light refracts

A image thumb
87

If angle of incidence = critical angle

Refracted ray travels along the surface of the denser medium

A image thumb
88

If angle of incidence > critical angle

Total Internal Reflection occurs

A image thumb