4 - Waves

Question 1

What is period (T)?

Answer 1

The time taken to complete one full oscillation

Question 2

What is the unit for period (T)?

Answer 2

seconds s

Question 3

What is frequency (f)?

Answer 3

The number of oscillations completed in 1 s

Question 4

What is the unit for frequency (f)?

Answer 4

Hertz Hz or s^-1

Question 5

What is amplitude (A)?

Answer 5

The maximum extent of an oscillation, measured from the point of equilibrium

Question 6

What is the unit for amplitude (A)?

Answer 6

metres m

Question 7

What determines the amount a ray will reflect?

Answer 7

the difference in density between two materials

the angle of the ray

Question 8

What is refractive index?

Answer 8

a property of a material that determines how much light will bend for a given angle of incidence

Question 9

What is diffraction?

Answer 9

when a wave passes through a narrow opening, it will behave as a point source and spread out in all directions

Question 10

Which of the following changes when a wave is refracted: wave speed, frequency or wavelength?

Answer 10

wave speed and wavelength change, but frequency remains the same

Question 11

What does the polarisation of light mean?

Answer 11

light waves (transverse) travel in different planes but with a polarising filter, all the wavelengths except the one travelling in the same plane are absorbed

Question 12

What is the principle of superposition?

Answer 12

when two or more waves meet, their instantaneous amplitudes add together

Question 13

When does constructive interference take place?

Answer 13

when two waves in phase interfere

the path difference between two identical waves is a whole number of wavelengths

Question 14

When does destructive interference occur?

Answer 14

when two waves out of phase interfere

the path difference between two identical waves is an odd number of half-wavelengths

Question 15

When will two waves stay in phase?

Answer 15

when they have the same frequency

Question 16

What is the phase difference when two waves are exactly antiphase?

Answer 16

1/2 a wavelength

Question 17

What is phase difference?

Answer 17

the lead or lag of one wave over the other

Question 18

What is the angle difference corresponding to a phase difference of wavelength/4?

Answer 18

90 degrees

Question 19

What is the angle difference corresponding to a phase difference of wavelength/2?

Answer 19

180 degrees

Question 20

What does Young’s double slit experiment show?

Answer 20

light behaves as a wave

Question 21

Why are two slits used?

Answer 21

to act as two light sources but with the same wavelength and frequency, so the light sources would be in phase
this means they would produce a constructive and destructive interference pattern

Question 22

What occurs at the first bright fringe?

Answer 22

light from both sources has travelled the same distance from each source
the two waves arrive in phase
they interfere constructively
bright fringe/ maximum produced

Question 23

What occurs at a dark fringe?

Answer 23

light from one slit has travelled exactly half a wavelength further than light from the other
the waves arrive exactly out of phase
they interfere destructively
dark fringe/ minimum produced

Question 24

How does an air molecule move in a longitudinal wave?

Answer 24

it is displaced to the left and right

Question 25

How do standing waves differ from travelling waves?

Answer 25

peak doesn’t travel for standing waves
standing waves can only have discrete frequencies
standing waves have nodes and antinodes
don’t propagate energy
travelling waves can have phase shifts
for standing waves, energy depends on position

Question 26

How do standing waves form?

Answer 26

wave travels down tube and is reflected
incident waves interferes with reflected wave
wave appears to be stationary