Waves Flashcards

1
Q

What can we use waves for?

A

Transmitting energy and information

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2
Q

What is the direction of travel of the wave the same as?

A

The direction in which the wave transfers energy

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3
Q

Describe a transverse wave

A

The oscillation (vibration) of the particles is perpendicular to the direction in which the wave travels

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4
Q

Describe a lonitudinal wave

A

The oscillation of the particles is parallel to the direction of the wave

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5
Q

Describe electromagnetic waves

A
  • Can travel through a vacuum
  • There are no particles moving, they are oscillations in electric and magnetic fields
  • Are transverse
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6
Q

Describe mechanical waves

A
  • E.g. waves on springs and sound waves
  • Travel through a medium (substance)
  • Can be transverse or longitudinal
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7
Q

Describe sound waves

A
  • Vibrations in the air/other media
  • These are eventually picked up by your ear, producing the sound
  • Longitundial
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8
Q

Aside from transverse and longitundal, what types of waves are there (and are they transverse or longitundinal)?

A
  • Electromagnetic - Transverse
  • Mechanical - Either
  • Sound - Longitundinal
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9
Q

Do longitudinal waves have an amplitude?

A

No

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10
Q

What is the amplitude of a wave?

A

The height of the wave crest or the depth of the wave trough from the position at rest

Greater amplitude = more energy

Defines the loudness of a sound wave (think of amps)

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11
Q

Complete the sentence:

The greater the amplitude of a wave…

A

…the more energy a wave has

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12
Q

What is the wavelength of a wave?

A

The distance from one crest to the next, or from one trough to the next

Measured in metres

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13
Q

What is the frequency of a wave?

A

The number of complete waves passing a set point per second

Measured in hertz (Hz) which is equivalent to per second

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14
Q

What is the wavelength of a longitudinal wave?

A

The distance from the middle of one compression/rarefaction to the next

(Instead of from one peak/crest/trough)

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15
Q

What is the frequency of a longitudianl wave?

A

The number of compressions passing a point per second

(As opposed to crests/troughs/peaks. Still complete waves)

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16
Q

What is meant by a plane mirror?

A

A flat mirror

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17
Q

When drawing a ray diagram, what should you always remember?

A

To draw the normal!

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18
Q

Where is the normal line drawn?

A

Perpendicular to the mirror/medium at the point where the incident ray hits the mirror

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19
Q

What does the law of reflection state?

A

That the angle of incidence is equal to the angle of reflection

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20
Q

What is the angle of incidence/reflection?

A

The angle between the incident/reflected ray and the normal

I.e. Not the medium/mirror!

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21
Q

Describe the image formed on a mirror

A
  • Same size as the object (not magnified/diminshed)
  • Upright
  • Same distance behind the mirror as the object is in front
  • Virtual
22
Q

What is a real image?

A

One that can be formed on a screen becayse the rays of light actually pass through it

23
Q

What is a virtual image?

A

Cannot be formed on a screen because the rays of light only appear to pass through it

24
Q

What changes when a wave crosses a boundary between different substances?

A

The speed and wavelength

The frequency stays the same

The wave also changes direction due to the change in speed

25
Q

Refraction is a property of what kind of wave?

A

All kinds

26
Q

What does the change in the speed of a wave cause?

A

A change in direction (refraction)

27
Q

What happens when light enters a more dense substance?

A

It slows down and bends towards the normal

28
Q

What happens when light enters a less dense substance?

A

It speeds up and bends away from the normal

29
Q

If light is travelling along the normal and enters a different substance, what will happen?

A

It will not change direction

30
Q

What is dispersion?

A
  • Different colours of light have different wavelengths
  • These are refracted by slightly different amounts when entering a different substance
  • When a ray of white light is shone onto a triangular prism we can see this because a spectrum is produced
  • Violet light is refracted the most, red light the least
31
Q

Why does light split up into different colours when it passes through a triangular prism?

A

Because the different wavelengths of light are refracted by different amounts

32
Q

What types of waves is diffraction a property of?

A

All waves

33
Q

What is diffraction?

A

The spreading out of waves when they pass through a gap/around an obstacle

It is most noticable if the wavelength of a wave is about the same size as the gap/obstacle

34
Q

Why don’t we often observe the diffraction of light during everyday life?

A

Because the wavelength of light is very short

35
Q

Why might someone get poor TV/mobile signal if they live in a hilly area?

A
  • These signals are carried by radio waves
  • These might be blocked by a hill
  • Radio waves will be diffracted around the hill
  • If they do not diffract enough, the signal will not reach the reciever aerial and will be poor
36
Q

Draw a diagram showing diffraction through a narrow and wide gap

A
37
Q

What causes sound?

A

Mechanical vibrations in a substance. It travels as waves

38
Q

What can sound travel through and at what speed (roughly)?

A

Can travel through solids, liquids, and gases.

It travels fastest in solids and slowest in gases

In other words, sound needs a medium through which to travel

39
Q

What can sound not travel through and how do we know this?

A

It cannot travel through a vacuum

This can be tested by listening to a ringing bell in a ‘bell jar’. If the air is pumped out of the jar, the sound fades away.

40
Q

What range of frequencies of sound can be heard by the human ear, and how does age affect this?

A

20Hx to 20,000Hz

The ability to hear higher frequencies declines with age

41
Q

What are the reflections of sound waves called?

A

Echoes

42
Q

What affects how/if echoes are produced?

A
  • Only hard, flat surfaces such as flat walls and floors reflect sound
  • Soft things like carpets, curtains, and furniture absorb sounds
  • An empty room will sound different once soft furnishings etc. are put into it/removed
43
Q

Where does the refraction of sound waves take place?

A

At the boundaries between layers of air at different temperatures

44
Q

What does the pitch of a note/sound depend upon?

A

The frequency of a wave

The higher the frequency, the higher the pitch

45
Q

What does the loudness of a note/sound depend upon?

A

The amplitude of a wave

The higher the amplitude, the louder the sound

This is because the wave carries more energy

(Think of amps)

46
Q

What does an oscilloscope show?

A

Waves + the differences in waveform (comparing waves)

47
Q

What can tuning forks and signal generators be used to produce?

A

‘Pure’ waveforms

48
Q

What does the quality of a note depend upon?

A

The waveform

49
Q

Why do different instruments not sound the same?

A

Because they produce different waveforms

50
Q

How do musical instruments produce sound?

A
  • Vibrations created in an instrument when it is played produce sound waves
  • In some instruments, e.g. saxophones, a column of air vibrates
  • In others, e.g. a violin, a string vibrates
  • Some instruments vibrate when they are struck, e.g. a xylophone