Waves 2

Question 1

What is a transverse wave?

Answer 1

A wave where vibrations occur perpendicular to the direction the wave is travelling

Question 2

What is a longitudinal wave?

Answer 2

A wave where vibrations occur parallel to the direction the wave is travelling

Question 3

Define amplitude

Answer 3

The maximum distance between the peak or trough of a wave and its equilibrium point

Question 4

Define wavefront

Answer 4

A horizontal line drawn linking all the peaks in a set of waves

Question 5

Define wavelength

Answer 5

The distance from point on a wave to the same point on the next wave

Question 6

Define frequency

Answer 6

Number of waves per second

Question 7

Define the period of a wave

Answer 7

Time taken to complete one wave cycle

Question 8

Equation for wave speed

Answer 8

Wave speed = frequency x wavelength

Question 9

Equation for wave frequency

Answer 9

Frequency = 1 / time period

Question 10

What property do all waves have in common?

Answer 10

They can be reflected and refracted

Question 11

What is the Doppler effect?

Answer 11

The change in frequency and wavelength caused by relative movement of the source of wave or observer

Question 12

Give an example of the Doppler effect in sound waves

Answer 12

• When an ambulance goes past you the siren decreases in pitch
• This is because the wavelength of the sound waves increases

Question 13

Give an example of the Doppler effect in light waves

Answer 13

• Light from distant planets looks red (it’s red-shifted)
• Because planets are moving away from us so wavelength becomes longer and therefore moves to the red spectrum

Question 14

Which EM waves can be used in cooking?

Answer 14

Microwaves and infrared radiation

Question 15

Which EM wave causes burns?

Answer 15

• Infra-red radiation

Question 16

Which EM wave causes skin cancer

Answer 16

UV

Question 17

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

Answer 17

• Ionising radiation
• Mutation
• Cancer

Question 18

What do all EM waves have in common?

Answer 18

• All transfer energy
• All travel at the same speed in a vacuum
• Can be reflected, refracted and diffracted
• All transverse waves

Question 19

What are the advantages of optic fibres?

Answer 19

• Carry more information per second
• More secure

Question 20

How are x-rays and gamma rays similar?

Answer 20

• Both short wavelength EM waves
• Carry lots of energy per second

Question 21

How do x-rays and gamma rays differ?

Answer 21

• X-rays are made when electrons moving at high speeds are stopped
• Gamma rays are released from unstable nuclei
• Gamma is more penetrative
• Gamma has shorter wave length

Question 22

Describe the properties of light waves

Answer 22

• Transverse wave
• Transfer energy
• Can be reflected, refracted, diffracted
• A wave where vibrations occur perpendicular to the direction the wave is travelling

Question 23

What is a normal line?

Answer 23

A line drawn perpendicular to the mirror

Question 24

What is the law of reflection?

Answer 24

• Angle of incidence = angle of reflection

Question 25

What is refraction?

Answer 25

A change in direction of waves when they travel across a boundary from one medium to another

Question 26

Describe how a light ray changes direction when it enters and leaves a glass block

Answer 26

- Bends towards the normal as it enters the block - Bends away from the normal as it leaves the block

Question 27

Snell's law (refractive index)

Answer 27

n = sin i / sin r

Question 28

Define critical angle

Answer 28

Angle of incidence beyond which rays of light are totally internally reflected

Question 29

Define total internal reflection

Answer 29

- When the angle of incidence is greater than the critical angle - All light is reflected, none is refracted

Question 30

How do optical fibres work?

Answer 30

- Total internal reflection - Core of fibre made out of glass with high refractive index - Cladding is made out of glass with lower refractive index - Light entering core is at an angle greater than the critical angle so light is TIR

Question 31

Give examples of the use of optical fibres

Answer 31

- Endoscope - used in keyhole surgery - Communication as less energy is lost when compared to using copper wiring

Question 32

Critical angle

Answer 32

sin c = 1 / refractive index (n)

Question 33

Describe the properties of sound waves

Answer 33

- Longitudinal waves - Transfer energy - Can be reflected, refracted and diffracted