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A - Physics GCSE > Topic 2 - Waves and the Electromagnetic spectrum > Flashcards

Topic 2 - Waves and the Electromagnetic spectrum Flashcards

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1
Q

What do waves transfer

A

energy and information

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2
Q

what are the differences between longitudinal and transverse waves

A

transverse waves are perpendicular to the direction of travel
longitudinal are parallel and trevel in a series of compressions and rarefactions

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3
Q

Give some examples of transverse and longitudinal waves

A

Transverse - light, S waves and all EM waves

Longitudinal - sound, P waves

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4
Q

what are the two equations used to find wave speed

A

frequency x wavelength

distance / time

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5
Q

How do you measure the velocity of sound in air

A

Using an oscilloscope -
attach 2 microphones to find wavelengths of sound wave generated.
-the wavelength is the distance between the microphones
-frequency is the signal generator

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6
Q

How do you measure the velocity of waves on a water surface

A

Using a strobe light and a signal generator attached to a dipper so waves are at set frequency
-distance between each shadow line is a wavelength

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7
Q

What is refraction

A

When a wave changed direction at a boundary

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8
Q

What happens when a wave goes from 1 material to another

A
  • When a wave hits at an angle it causes a change of speed
  • so when it hits a glass block for example it changes direction
  • when entering it bends towards the normal
  • when leaving it bends away from the normal
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9
Q

what does it mean if a wave is reflected

A

when a wave is neither absorbed or transmitted but sent back away from the second material
eg) echos

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10
Q

What are the effects of waves being transmitted or absorbed

A
  • waves transfer energy to energy stores - absorption

- when waves carry on travelling through a new material they are transmitted

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11
Q

what are the parts of the human ear

A

sound waves travel down

  • ear canal
  • osscicles
  • through semi circular canal
  • cochlea
  • auditory nerve to brain
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12
Q

how are sound waves converted to vibrations in solids (in the ear)?

A

When sound waves hit the cochlea it causes them to vibrate and turns them into vibrations which go down the ear. The structure and shape of our eardrum effects this

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13
Q

Why can the human ear only detect a certain range of frequencies

A

Because the frequencies above 20,000 Hz and below 20 Hz are too high/low pitch to be detected

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14
Q

How can you calculate the depth of water with time and wave velocity

A
  • send signals from boat and measure how long it takes to come back
  • half this time as we only want one way
  • use wavelength = wavespeed x time
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15
Q

What is ultrasound

A

any frequency above 20,000 Hz

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16
Q

How is ultrasound used in sonar

A

It can be used in echo-sounding to detect how deep the oceans are

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17
Q

How is ultrasound used in foetal scanning

A

As ultrasound can pass through the body, it can reflect back off the womb and skin of the foetus
these signals can be detected on a computer to produce an image

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18
Q

What is infrasound

A

Any frequency below 20Hz

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19
Q

Name some uses of infrasound

A
  • animal tracking for whales and elephants

- detect natural disasters such as earthquakes from their seismic waves- these are monitored by scientists

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20
Q

What type of wave are seismic waves

A

infrasound

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21
Q

What is the difference between P and S waves

A

P waves - longitudinal, travel through solids and liquids and and faster than S waves

S waves - transverse, travel through Solids and are slower than P waves

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22
Q

How do seismic waves help us investigate the earths core

A

Only Pwaves can travel through the earths outer core which means it must be a liquid/ molten and the earths core is Solid.

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23
Q

What is the law of reflection

A

Angle of incidence = angle of reflection

24
Q

What is total internal reflection

A
  • Depends on the critical angle

- only happens when angle of incidence is larger than the critical angle so no light comes out

25
Q

What is the difference between specular and diffuse reflection

A

Specular- waves are reflected in a single direction by a smooth surface so you get a clear reflection

Diffuse- On rough/matt surfaces, waves are reflected in all directions as the normal is different for each incident waves

26
Q

What is white light

A

A mixture of all different colours of light which have different wavelengths

27
Q

Why do surfaces appear to have different colours in terms of differential absorption

A

Because it depends on which wavelengths of light are reflected
eg) red apple reflects red

28
Q

How do filters make coloured light

A

They filter out different wavelengths of light in terms of transmission and absorb these colours
eg)red light»» blue filter =black

29
Q

How does viewing of different coloured objects differ in other colours of light
with red apple, green pear, blueberry

A
  • red apple- blue and green light makes black, red stays red
  • green pear- blue makes blue, green=green, red light=black
  • blueberry- blue= blue, green= cyan red=black
30
Q

What does the power of a lens mean

A

As the power of a lens increases, it bends light through a greater angle

31
Q

How does the focal length effect the shape and power of a lens

A

more powerful= more strongly converging light=shorter focal length

Power of a lens increases with its curvature

32
Q

How does a converging lens refract light

A

-light rays hit a convex lens and refract/bend towards the normal
-and when leaving the lens come together to form a real image on a screen
(Positive power)

33
Q

How does a diverging lens refract light

A
  • as the light rays enter they spread out/ diverge and create a virtual image which appears to come from a different direction
  • and if we trace the rays back we find the virtual principal focus
34
Q

How do we find the focal length

A

distance between the virtual principle focus and lens

35
Q

What are all 7 Electromagnetic Waves

A

Radio, micro, infrared, visible light, ultraviolet, X-ray, Gamma

36
Q

Name some features of EM waves

A

Transverse
Travel at same speed in a vacuum
Transfer energy from source to observer
Higher frequency = more energy transferred

37
Q

How do we group EM waves

A

based on there frequencies and wavelengths

38
Q

What effects energy transfer in EM waves

A

Higher frequency = more energy transferred

39
Q

What range of EM waves can our eyes detect

A

Visible light

40
Q

What is the order of the visible light spectrum

A

Red, orange, yellow, green, blue, indigo, violet

41
Q

How do velocities of EM waves differ in different substances

A
  • Vacuum all the same
  • Other materials - shorter the wavelength the more it bends to change direction and the slower it is
    eg) light travels slower in denser materials, radio not as much

frequency is the same + wavelength slower

42
Q

Name some different ways EM waves are absorbed and transmitted

A
  • Radiowaves arent absorbed by the body
  • Gamma can be absorbed by deeper tissues
  • UV is absorbed by skin and can cause damage to cells
  • UV is absorbed by Earths atmosphere
  • Some materials absorb light wavelength of one colour but not others causing them to be a certain colour
43
Q

How are radiowaves affected by travelling through different substances

A
  • transmitted through body
  • not harmful if absorbed
  • can be reflected and change direction
44
Q

Name some uses of Radiowaves

A

communication and broadcasting

45
Q

Name some uses of Microwaves

A

microwaves, communication by satellite

46
Q

Name some uses of Infrared

A

T.V remotes, infrared cameras

47
Q

Name some uses of Visible Light

A

photography film, cameras

48
Q

Name some uses of UV

A

fluorescent lamps, security pens

49
Q

How are radiowaves produced and detected by electrical circuits

A

Radiowaves are produced by oscillating charges creating alternating currents.
This energy is transferred to the electrons in the material of the reciever

50
Q

How does the intensity and wavelengths of emitted radiation depend on the temperature of the body

A
  • When intensity increases rapidly for shorter wavelengths. The rate an object radiates EM radiation affects its temperature
  • object at a constant temperature radiates and absorbs the same average power
51
Q

Name a use of X-rays

A

airport security scanners

52
Q

Name some uses of gamma rays

A

sterilising medical instruments, cancer treatment

53
Q

How does the danger of EM radiation depend on its frequency

A

The higher the frequency the more dangerous it is because it transfers more energy

54
Q

What are the harmful effects of infrared

A

infrared can cause burning

55
Q

Danger of UV

A

skin cancer

56
Q

Dangers of X-Ray

A

too much exposure puts you at risk of cancer

57
Q

Dangers of Gamma

A

damages cells and causes mutations which can lead to cancer

A - Physics GCSE (9 decks)

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