Unit 2 - Waves

Question 0

A scientist discovers a seismic wave that is polarised. State and explain what can be deduced from this. (2)

Answer 0

• Transverse

* Only transverse waves can be polarised

Question 1

What two conditions are required for total internal reflection. (2)

Answer 1

• n1 > n2

* Angle > critical angle

Question 2

Define the frequency of a progressive wave. (1)

Answer 2

• Number of waves passing a point per second

Question 3

Explain the meaning of the term monochromatic light. (1)

Answer 3

Single frequency or wavelength

Question 4

State and explain one precaution that should be taken when using laser light. (2)

Answer 4

• Don’t shine towards person/ avoid reflections

* Causes eye damage

Question 5

Give two reasons why optical fibres used for communications have cladding. (2)

Answer 5

(Any two)

Protect core from scratching/ prevent crossover of signal/ increase critical angle/ reduce multipath dispersion

Question 6

Explain what is meant by coherent sources. (2)

Answer 6

• Same wavelength/ frequency

* Constant phase relationship/ phase difference

Question 7

What surrounds optical fibres.? (1)

Answer 7

Cladding

Question 8

State and explain one advantage associated with a smaller diameter core. (2)

Answer 8

(Any two)
Less light lost/ less multipath dispersion/ better quality signal/ better probability of TIR/ less refraction out of the core

Question 9

What is the point of maximum displacement called on a stationary wave? (1)

Answer 9

Antinode

Question 10

Explain why it is important to correctly align the aerial of a TV aerial in order to receive the strongest signal. (2)

Answer 10

• Transmitted radio waves polarised

* Aerials must be aligned in same plane as polarised waves

Question 11

State and explain one reason why an optical fibre is made as narrow as possible. (2)

Answer 11

• To reduce multipath dispersion

* Which would cause light to arrive at different times/ merge adjacent puzzles

Question 12

State one application of optical fibres and explain how this has benefited society. (2)

Answer 12

Application - endoscope
Benefit - improved medical diagnosis

Application - communications
Benefit - improve data transmission

Question 13

How do you increase the fundamental frequency. (1)

Answer 13

Decrease the length/ increase tension/ tighten string

Question 14

What did Young’s double slit experiment suggest about the nature of light. (1)

Answer 14

Showed light was a wave

Question 15

State what is meant by monochromatic. (1)

Answer 15

Single wavelength (frequency)

Question 16

State what is meant by coherent. (1)

Answer 16

Wave source has constant phase difference

Question 17

State one safety precaution that should be taken when using a laser. (1)

Answer 17

Do not look into laser/ laser safety goggles/ don’t point laser at others

Question 18

A laser is replaced by another laser emitting visible light with a shorter wavelength. State and explain how this will affect the spacing of the maxima on the screen. (2)

Answer 18

• Maxima closer together

* Spacing is proportional to wavelength as D and s are constant therefore as λ decreases maxima width decreases

Question 19

Define the amplitude of a wave. (1)

Answer 19

Maximum displacement from equilibrium

Question 20

Other than electromagnetic radiation, give one example of a wave that is transverse. (1)

Answer 20

Rope/ water ripples/ secondary S waves

Question 21

State one difference between a transverse wave and longitudinal wave. (1)

Answer 21

(Any one)
• transverse’s oscillations perpendicular to energy
• transverse can be polarised
• longitudinal require a medium

Question 22

State one application of a polarising filter and give a reason for its use. (2)

Answer 22

• • Polaroid glasses - reduce glare
• • Camera - reduce glare
• • Microscopes - to identify minerals
• • 3D glasses - enhance viewing experience

Question 23

Describe how the pattern of a single slit light intensity graph would change if light of a longer wavelength was used. (1)

Answer 23

Maxima further apart

Question 24

State two ways in which the appearance of the fringes would change if the slit was made narrower. (2)

Answer 24

• Wider separation

* Lower intensity

Question 25

explain why total internal reflection doesn’t occur when a ray travels from water to glass. (1)

Answer 25

TIR only when ray travels from higher n to lower n