Waves - Paper 2

Question 1

What do waves transfer?

Answer 1

Energy

Question 2

What are the two types of wave?

Answer 2

Transverse and longitudinal

Question 3

Describe a transverse wave

Answer 3

The vibrations of the wave are perpendicular** to the direction in which **energy is transferred.

Question 4

Give some examples of transverse waves

Answer 4

Ripples on a water surface

Any wave in the electromagnetic spectrum

S waves

Question 5

Describe a longitudinal wave

Answer 5

The vibrations of the wave are parallel** to the direction in which **energy is transferred.

Longitudinal waves show areas of compression** and **rarefaction.

Question 6

Give some examples of longitudinal waves

Answer 6

Sound waves

Ultrasound

P waves

Question 7

Define amplitude

Answer 7

The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position.

It shows us how much energy a wave has.

Question 8

Define wavelength

Answer 8

The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave. Measured in meters

Question 9

Define frequency

Answer 9

It is the number of waves that pass a point per second. Measured in hertz (Hz)

Question 10

Define period (T)

Answer 10

Its the time for one exact wave to pass a point. Measured in seconds

T = 1 / f

Question 11

State the wave equation with all units

Answer 11

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

Question 12

Describe an experiment to find the speed of sound through air

Answer 12

1. Measure a distance of 100 m from a wall.
2. Hit two blocks together to make a sound and start timing.
3. Stop timing when the hear the reflected sound (echo).
4. Divide the time recored by 2 as the sound has travelled to the wall and back again
5. use the equation Speed = distance / time

Question 13

Describe a method to measure the speed of ripples on a water surface.

Answer 13

1. Set up a ripple tank.
2. Find the wavelength by using a ruler to measure across 10 wavelengths.
3. Divide the answer by 10 to find 1 wavelength.
4. Use a stopwatch and count the number of waves produced in 10 seconds.
5. Dived the answer by 10 to find the frequency.
6. Use the equation speed = wavelength x frequency

Question 14

What can happen to waves when they reach a boundary between two materials?

Answer 14

1. They can be reflected
2. They can be absorbed (this will cause a small temperature rise)
3. They can be transmitted (they will pass through)

Question 15

What is the law of reflection

Answer 15

The angle of incident = angle of reflection for a flat plain mirror.

Question 16

What is refraction?

Answer 16

When a wave travels from one medium to another and changes direction.

Question 17

Why does refraction take place?

Answer 17

The change in medium means a change in density which caused a change in speed.

Question 18

When a substance moves from a more dense to a less dense substance, what is the affect of waves speeds, frequency and wavelength?

Answer 18

1. Wave speed - decreases
2. Frequency - same
3. Wavelength - decreases

Question 19

When a substance moves from a less dense to a more dense substance, what is the affect of waves speeds, frequency and wavelength?

Answer 19

1. Wave speed - increases
2. Frequency - same
3. Wavelength - increases

Question 20

When light slows down which direction does it refract?

Answer 20

Towards the normal

Question 21

When light speeds up which direction does it refract?

Answer 21

Away from the normal

Question 22

Explain why light refracts as it passes from air into glass?

Answer 22

As light moves from air into glass it slows down.

The edge of the wave front entering the glass first slows down first

Part of the wave front that is still in the air continues at a higher speed causing it to travel further and to change in direction

Question 23

What do all electromagnetic waves have in common?

Answer 23

1. They are all transverse waves
2. They can all travel through a vacuum
3. They all travel at the speed of light through a vacuum

Question 24

How are radio waves produced?

Answer 24

By an oscillating electrical current in the transmitter. The frequency of the current will make the frequency of the radiowaves.

Question 25

What happens when radio waves are absorbed by an aerial?

Answer 25

When radio waves are absorbed they will create an alternating current with the same frequency as the radio wave itself

Question 26

What are the dangers of ultraviolet waves

Answer 26

1. Can age skin prematurely
2. Can burn skin which can lead to skin cancer
3. Damage eyes which can lead to blindness

Question 27

What are the dangers of X-rays and gamma rays?

Answer 27

X-rays and gamma rays are ionising radiation.

Low doses can damage DNA and cause cancer

Large doses can kill cells

Question 28

State some uses of radio waves

Answer 28

television and radio, these waves stay within the earths atmosphere.

Question 29

State some uses of microwaves

Answer 29

Satellite communications eg mobile phone and satellite TV. Microwaves can travel to space and back.

Cooking food.

Question 30

State some uses of infrared

Answer 30

electrical heaters, cooking food, infrared cameras

Question 31

State some uses of visible light

Answer 31

fibre optic communications

Question 32

State some uses of ultraviolet

Answer 32

energy efficient lamps

sun tanning

security markings

Question 33

State some uses of X-rays and Gamma rays

Answer 33

medical imaging and cancer treatment.

Question 34

Describe how x-rays are used for medical imaging

Answer 34

pass through soft tissue

but are absorbed by bone