P4 - Properties of waves, including light and sound

Question 1

Waves have a

Answer 1

wavelength, frequency, amplitude, and time period.

Question 2

What is the wavelength of the wave

Answer 2

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

Question 3

What is frequency

Answer 3

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

Question 4

What is the amplitude

Answer 4

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

Question 5

What is speed of wave

Answer 5

the distance the wave travels in 1 s.

Question 6

What does the speed of a wave depend on

Answer 6

1. The substance

2. The medium the wave is passing through

Question 7

Waves transfer energy from one place to another without

Answer 7

transferring matter

Question 8

What is wave motion

Answer 8

The movement of a wave

Question 9

Wave motion can be shown by

Answer 9

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

2. 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.

Question 10

What is a wavefront

Answer 10

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

Question 11

What are the two types of waves

Answer 11

longitudinal and transversal waves

Question 12

In a longitudinal wave vibrations are

Answer 12

in the direction of travel of the wave.

It can be shown by pushing and pulling a spring

Question 13

The stretching of a sling produces

Answer 13

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

Question 14

What is an example of a longitudinal wave

Answer 14

sound

Question 15

How is the wavelength found in a longitudinal wave

Answer 15

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

Question 16

In a transverse wave vibrations are

Answer 16

at right angles to the direction of wave travel.

It can be shown by moving a spring side to side

Question 17

Examples of transverse wages

Answer 17

Light

radio and other electromagnetic waves

Question 18

What are the similarities of transverse and longitudinal waves

Answer 18

Similarities

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

Question 19

The speed of a wave in a given medium is

Answer 19

constant

Question 20

What is the equation for wave speed

Answer 20

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

Question 21

Reflection happens when

Answer 21

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

Question 22

Refraction is when a

Answer 22

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

Question 23

When a wave crosses a new medium at an angle

Answer 23

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

Question 24

What is diffraction

Answer 24

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

Question 25

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

Answer 25

with little diffraction

Question 26

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

Answer 26

increases and not much of the waves will pass through.

Question 27

Diffraction is strongest and most noticeable when

Answer 27

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

Question 28

The angle of the incidence is the angle

Answer 28

between the incident (incoming) light ray and the normal

Question 29

The normal is

Answer 29

perpendicular (90) to the surface of the plane

Question 30

The angle of reflection is the angle

Answer 30

between the reflected light ray and the normal

Question 31

What does the law of reflection state

Answer 31

that an angle of incidence = the angle of reflection

Question 32

When a wave slows down

Answer 32

the wavelength gets smaller

Question 33

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

Answer 33

denser medium

Question 34

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

Answer 34

also decrease

Question 35

When a wave speeds up

Answer 35

the wavelength gets larger

Question 36

If speed increases but frequency stays the same the wavelength must

Answer 36

also increase

Question 37

Why does light not need a medium to travel through

Answer 37

Because it is an electromagnetic wave

Question 38

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

Answer 38

laterally inverted (left and right sides are exchanged)

Question 39

What is a virtual image

Answer 39

is something that cannot be projected onto a screen

Question 40

Light waves slow down when they travel from

Answer 40

air to glass

Question 41

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

Answer 41

bends toward the normal as they enter the glass

Question 42

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

Answer 42

increases and they bend away from the normal

Question 43

What is the refractive index

Answer 43

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

Question 44

What is the equation of the refractive index

Answer 44

n = sin i/ sin r

Question 45

The refractive index of a vacuum is

Answer 45

1

Question 46

what is another equation of the refractive index

Answer 46

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

Question 47

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

Answer 47

bend away from the normal

Question 48

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

Answer 48

critical angle

Question 49

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

Answer 49

reflects back inside the material

Question 50

What is total internal reflection

Answer 50

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

Question 51

critical angle formula

Answer 51

n = 1/sin c

Question 52

total internal reflection is used in

Answer 52

fibre optic cables

Question 53

Light does not escape from the fibre because

Answer 53

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

Question 54

Why are fibre optic cables useful and used

Answer 54

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