P4 - Properties of waves, including light and sound Flashcards

1
Q

Waves have a

A

wavelength, frequency, amplitude, and time period.

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2
Q

What is the wavelength of the wave

A

it is the distance between two adjacent peaks or troughs of waves.

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3
Q

What is frequency

A

Frequency is the number of complete waves that go past each second (Hz)

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4
Q

What is the amplitude

A

in a water wave it is the maximum displacement of the water from an undisturbed position.

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5
Q

What is speed of wave

A

the distance the wave travels in 1 s.

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6
Q

What does the speed of a wave depend on

A
  1. The substance

2. The medium the wave is passing through

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7
Q

Waves transfer energy from one place to another without

A

transferring matter

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8
Q

What is wave motion

A

The movement of a wave

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9
Q

Wave motion can be shown by

A
  1. vibrations of a spring
    Hold one end of a horizontal spring in a fixed position and move the other end of the spring up and down

We can observe a wave moving from the end we are holding towards the fixed end of the spring

  1. water wave
    When a wave travels along the surface of a water, a cork floating on the surface will only move up and down as waves pass.
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10
Q

What is a wavefront

A

it is a moving line that joins all points on the crest of a wave

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11
Q

What are the two types of waves

A

longitudinal and transversal waves

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12
Q

In a longitudinal wave vibrations are

A

in the direction of travel of the wave.

It can be shown by pushing and pulling a spring

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13
Q

The stretching of a sling produces

A

regions of rarefaction (where the coils spread out) and regions of compression (where the coil is squashed).

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14
Q

What is an example of a longitudinal wave

A

sound

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15
Q

How is the wavelength found in a longitudinal wave

A
  1. Where the distance between two consecutive points of maximum compression
  2. Distance between two consecutive points of minimum compression.
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16
Q

In a transverse wave vibrations are

A

at right angles to the direction of wave travel.

It can be shown by moving a spring side to side

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17
Q

Examples of transverse wages

A

Light

radio and other electromagnetic waves

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18
Q

What are the similarities of transverse and longitudinal waves

A

Similarities

  1. Both made up of vibrations
  2. They both are waves that have repeating shape or pattern
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19
Q

The speed of a wave in a given medium is

A

constant

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20
Q

What is the equation for wave speed

A

wave speed (m/s) = frequency (Hz) x wavelength (m)

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21
Q

Reflection happens when

A

a wave hits a flat surface (plane) and bounces off it

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22
Q

Refraction is when a

A

waves speed can change when moving from one medium to another.

23
Q

When a wave crosses a new medium at an angle

A

the change in a wave’s speed will cause the direction of the wave’s motion to change and the wave will appear to bend

24
Q

What is diffraction

A

when a wave reaches a narrow gap in a surface they will continue to travel through that gap and change shape.

25
Q

If the gap size is relatively large compared to the wavelength the wave passes

A

with little diffraction

26
Q

If the gap size is relatively small compared to the wavelength the amount of diffraction

A

increases and not much of the waves will pass through.

27
Q

Diffraction is strongest and most noticeable when

A

the width of the gap is similar in size to the wavelength of the wave.

28
Q

The angle of the incidence is the angle

A

between the incident (incoming) light ray and the normal

29
Q

The normal is

A

perpendicular (90) to the surface of the plane

30
Q

The angle of reflection is the angle

A

between the reflected light ray and the normal

31
Q

What does the law of reflection state

A

that an angle of incidence = the angle of reflection

32
Q

When a wave slows down

A

the wavelength gets smaller

33
Q

A wave slows down as it travels across the boundary to a

A

denser medium

34
Q

If frequency of a wave does not change crossing the boundary and the speed creases the wavelength must

A

also decrease

35
Q

When a wave speeds up

A

the wavelength gets larger

36
Q

If speed increases but frequency stays the same the wavelength must

A

also increase

37
Q

Why does light not need a medium to travel through

A

Because it is an electromagnetic wave

38
Q

When you look in a plane mirror the image you see is called

A

laterally inverted (left and right sides are exchanged)

39
Q

What is a virtual image

A

is something that cannot be projected onto a screen

40
Q

Light waves slow down when they travel from

A

air to glass

41
Q

When a light ray is at an angle to a glass it

A

bends toward the normal as they enter the glass

42
Q

When light rays travel out of the glass into air their speed

A

increases and they bend away from the normal

43
Q

What is the refractive index

A

it indicates how much the material changes the direction of the light

44
Q

What is the equation of the refractive index

A

n = sin i/ sin r

45
Q

The refractive index of a vacuum is

A

1

46
Q

what is another equation of the refractive index

A

n = speed of light in vacuum (or air) / speed of light in the material

47
Q

When rays of light pass from a dense medium to a less dense medium they

A

bend away from the normal

48
Q

the angle of incidence at which the angle of refraction becomes equal to 90 is called the

A

critical angle

49
Q

when the angle of incidence surpasses the critical angle the angle of refraction

A

reflects back inside the material

50
Q

What is total internal reflection

A

when the angle of incidence is greater than the critical angle so the rays are entirely reflected back inside the medium

51
Q

critical angle formula

A

n = 1/sin c

52
Q

total internal reflection is used in

A

fibre optic cables

53
Q

Light does not escape from the fibre because

A

it always hits the internal surface at an angle greater than the critical angle and is internally reflected

54
Q

Why are fibre optic cables useful and used

A

They do not use electricity so signals can be carried by infrared waves and do not suffer interference.

They are cheaper than copper cables and can carry thousands of different signals down the same fibre

Bundles of several thousand optical fibers used in medical endoscopes for internal examination of body