4 - Waves Flashcards

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1
Q

What is period (T)?

A

The time taken to complete one full oscillation

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2
Q

What is the unit for period (T)?

A

seconds s

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3
Q

What is frequency (f)?

A

The number of oscillations completed in 1 s

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4
Q

What is the unit for frequency (f)?

A

Hertz Hz or s^-1

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5
Q

What is amplitude (A)?

A

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

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6
Q

What is the unit for amplitude (A)?

A

metres m

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7
Q

What determines the amount a ray will reflect?

A

the difference in density between two materials

the angle of the ray

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8
Q

What is refractive index?

A

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

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9
Q

What is diffraction?

A

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

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10
Q

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

A

wave speed and wavelength change, but frequency remains the same

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11
Q

What does the polarisation of light mean?

A

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

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12
Q

What is the principle of superposition?

A

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

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13
Q

When does constructive interference take place?

A

when two waves in phase interfere

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

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14
Q

When does destructive interference occur?

A

when two waves out of phase interfere

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

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15
Q

When will two waves stay in phase?

A

when they have the same frequency

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16
Q

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

A

1/2 a wavelength

17
Q

What is phase difference?

A

the lead or lag of one wave over the other

18
Q

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

A

90 degrees

19
Q

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

A

180 degrees

20
Q

What does Young’s double slit experiment show?

A

light behaves as a wave

21
Q

Why are two slits used?

A

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

22
Q

What occurs at the first bright fringe?

A

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

23
Q

What occurs at a dark fringe?

A

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

24
Q

How does an air molecule move in a longitudinal wave?

A

it is displaced to the left and right

25
Q

How do standing waves differ from travelling waves?

A

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

26
Q

How do standing waves form?

A

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