Waves

Question 1

Unit for angle

Answer 1

degree (°)

Question 2

Unit for frequency

Answer 2

hertz (Hz)

Question 3

Unit for wavelength

Answer 3

metre (m)

Question 4

Unit for velocity

Answer 4

metre/second (m/s)

Question 5

Unit for time

Answer 5

second (s)

Question 6

Explain the movement of a longitudinal wave

Answer 6

Longitudinal waves is a wave that vibrates or oscillates at parallel to (along) the direction in which the wave is moving.

Question 7

Explain the movement of a tranverse wave

Answer 7

Transverse waves is a wave that vibrates or oscillates at right angles (perpendicular) to the direction in which the wave is moving.

Question 8

Explain the difference between a transverse wave and a longitudinal wave

Answer 8

A longitudinal wave has vibrations parallel to the direction of the wave meanwhile transverse waves has vibrations at right angles to the direction of the wave

Question 9

Wavefront

Answer 9

A way of seeing waves from above

Question 10

Amplitude

Answer 10

This is the distance from the midpoint to the peak of a wave

Question 11

Wavelength

Answer 11

This is the distance between two corresponding points on the wave and is measured in metres

Question 12

Frequency

Answer 12

This is how many waves pass by a point every second and is measured in Hertz (Hz)

Question 13

Time period

Answer 13

The time it takes for one complete wave to pass a particular point

Question 14

What can waves transfer?

Answer 14

Waves can transfer energy and information with out transferring matter

Question 15

Give an example of a wave that transfers energy

Answer 15

Sun light, it transfers energy as it makes the earth warm without bringing any matter.

Question 16

What is the relationship between the speed, frequency and wavelength of a wave: v = f × λ

Answer 16

Wave speed (v) = frequency (f) x wavelength (λ)

Question 17

Give the units for the wave equation

Answer 17

Wave speed (m/s) = frequency (Hz) x Wavelength (m)

Question 18

What is the relationship between frequency and time period: time period x frequency = 1 or f = 1/T

Answer 18

Time period(T) = 1 / frequency (f)
Frequency (f) = 1 / time period (T)
1 = frequency (f) x time period (T)

Question 19

Doppler effect

Answer 19

When an object is moving toward you the waves from the object compress and you hear this as a higher frequency. When an object is moving away from you the waves strech out and you hear this as a lower frequency. The greater the speed of the moving object the greater the change in frequency. The sound the leaves the speaker is always the same, it is only different to the observer

Question 20

Properties of electromagnetic waves

Answer 20

Transfer energy
Are transverse waves
Travel at the speed of light in a vacuum
Can be reflected and refracted

Question 21

Electromagnetic waves (from low to high frequency)

Answer 21

Radio waves
Micro waves
Infra red 
Visible light
Ultra-violet 
X-rays 
Gamma rays

Question 22

Uses of Radio waves

Answer 22

broadcasting and communications

Question 23

Uses of Microwaves

Answer 23

cooking and satellite transmissions

Question 24

Uses of infra red

Answer 24

remote controls and night vision equipment

Question 25

Uses of visible light

Answer 25

optical fibres and photography

Question 26

Uses of ultraviolet

Answer 26

fluorescent lamps and killing bacteria

Question 27

Uses of X-rays

Answer 27

observing the internal structure of objects and materials, including for medical applications

Question 28

Uses of gamma rays

Answer 28

sterilising surgical equipment and medical equipment

Question 29

Danger of microwaves

Answer 29

internal heating of body tissue

Question 30

Danger of infrared

Answer 30

skin burns

Question 31

Danger of ultraviolet and protective measures

Answer 31

damage to surface cells and blindness; wear sun glasses, sun cream and stay in shade for UV

Question 32

Danger of gamma rays and protective measures

Answer 32

cancer, mutation; avoid exposure and wear suitable protective clothing

Question 33

Light is...

Answer 33

a transverse wave and can be reflected and refracted

Question 34

Reflection

Answer 34

When light reflects off a mirror the angle of incidence always equals the angle of reflection

Question 35

Refraction

Answer 35

When light enters a medium of different density is changes speed and direction. This change in direction is known as refraction

Question 36

The role of total internal reflection

Answer 36

Total internal reflection is used to transmit signals along optical fibres.

Question 37

When happens refraction

Answer 37

angle of incidence < critical angle

Question 38

When happens critical case

Answer 38

angle of incidence = critical angle

Question 39

When happens TIR

Answer 39

angle of incidence > critical angle

Question 40

What is required for TIR to occur

Answer 40

The ray of light must be travelling from a more dense to a less dense medium. The angle of incidence must be greater than the critical angle.

Question 41

Snell's law

Answer 41

n = sin i / sin r

Question 42

Critical angle

Answer 42

When light is refracted and passes along the boundary of the surface

Question 43

The relationship between critical angle and refractive index

Answer 43

``` C = sin-1(1/n) n = 1 / sinC ```

Question 44

longitudinal waves can...

Answer 44

be reflected and refracted

Question 45

Practical to find the refractive index and the critical angle of a glass block

Answer 45

1. Set up your apparatus as shown in the diagram using a rectangular block. 2. Shine the light ray through the glass block 3. Use crosses to mark the path of the ray. 4. Join up crosses with a ruler 5. Draw on a normal where the ray enters the glass block 6. Measure the angle of incidence and the angle of refraction and add these to your results table 7. Calculate the refractive index 8. Repeat steps 2 – 7 using a different angle of incidence 9. Find an average of your results.