Waves

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

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

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

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

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

Question 13

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

Answer 13

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

Question 14

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

Answer 14

They can be reflected
They can be absorbed (this will cause a small temperature rise)
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

Wave speed - decreases
Frequency - same
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

Wave speed - increases
Frequency - same
Wavelength - increases

Question 20

State the waves that make up the electromagnetic spectrum, in order of increasing wavelength

Answer 20

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays

Question 21

What do all electromagnetic waves have in common?

Answer 21

They are all transverse waves
They can all travel through a vacuum
They all travel at the speed of light through a vacuum

Question 22

How are radio waves produced?

Answer 22

By an oscillating electrical current.

Question 23

What happens when radio waves are absorbed by an aerial?

Answer 23

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

Question 24

What are the dangers of ultraviolet waves

Answer 24

Can age skin prematurely
Can burn skin which can lead to skin cancer
Damage eyes which can lead to blindness

Question 25

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

Answer 25

X-rays and gamma rays are ionising radiation
Low doses can damage DNA and cause cancer
Large doses can kill cells

Question 26

State some uses of radio waves

Answer 26

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

Question 27

State some uses of microwaves

Answer 27

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

Question 28

State some uses of infrared

Answer 28

electrical heaters, cooking food, infrared cameras

Question 29

State some uses of visible light

Answer 29

fibre optic communications

Question 30

State some uses of ultraviolet

Answer 30

energy efficient lamps, sun tanning

Question 31

State some uses of X-rays and Gamma rays

Answer 31

medical imaging and treatments.