1
Q
What is a waves displacement on a progressive wave
A
How far a point on the wave has moved from its undisturbed position
2
Q
What is the amplitude of a wave
A
The maximum magnitude of the displacement
3
Q
What is the wavelength of a progressive wave
A
The length of one whole wave cycle, from crest to crest
4
Q
What is a waves period (T)
A
Time taken for a whole cycle to complete
5
Q
What is the frequency of a wave
A
The number of cycles per second passing a given point
6
Q
What is a phase
A
A measurement of the position of a certain point along the wave cycle
7
Q
What is a phase difference
A
Difference between the same point of 2 different waves in radians
Measure in pi
8
Q
Equation linking frequency and time period
A
f=1/T
9
Q
What is frequency measured in
A
Hertz (Hz)
10
Q
What is 1Hz equal to
A
1s^-1
11
Q
Equation linking frequency, wave length and wave speed
A
Wave speed= f x wavelength
12
Q
what does a cathode ray oscilloscope (CRO) measure?
A
Voltage
13
Q
2 types of waves
A
Transfers and longitudinal
14
Q
Axis of graphs of transverse waves
A
x= displacement
y= distance
OR
y= time
15
Q
What is a transverse wave
A
A wave where the particles oscillate perpendicular to the direction the wave propagates
16
Q
What is a longitudinal wave
A
A wave where the particles oscillate parallel to the direction the wave propagates
17
Q
Examples of longitudinal waves
A
Sound
18
Q
what are the condensed and separated areas called on longitudinal waves
A
Compressions and rarefactions
19
Q
Examples of transfers waves
A
All electromagnetic waves, x rays, gamma rays, UV etc
20
Q
What is intensity
A
The rate of flow of energy per unit area , perpendicular to the direction of travel of the wave
21
Q
What is intensity measured in
A
Wm-2
22
Q
Equation for intensity
A
Intensity= power/area
23
Q
Why is intensity proportional to
A
amplitude squared
24
Q
Why is intensity proportional to amplitude squared
A
-intensity is proportional to energy
-the energy of a wave depends on the square of the amplitude
25
Axis of longitudinal graphs
x= displacement
y= time
26
Equation linking frequency, wave speed and wavelength
V=f λ
27
Can longitudinal waves be polarised
No
28
Can transverse waves be polarised
Yes
29
Order of EM waves largest to smallest
Radio
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
30
Approx wavelength of radio, microwaves, infrared, visible, UV, X-rays, gamma
Radio: 10 ³
Microwaves: 10-²
Infrared: 10-⁵
Visible: 10-⁷
UV: 10-⁸
X-rays: 10-¹¹
Gamma: -¹⁴
31
Does a polarised wave oscillate in one or many directions
One
32
Investigation polarisation of light:
1. Shine … white light through 2 …
2. A… the filters so they are …, then shine light through the first filter and … the second filter
3. The light passed through the first filter is … polarised
4. As the 2nd filter is … less light will get through its … component so its intensity …
5. When the filters are at 45° to eac other the intensity will be …, if they are at 90° the intensity is …
1. Shine unpolarised white light through 2 filters
2. Align the filters so they are vertical, then shine light through the first filter and rotate the second filter filter
3. The light passed through the first filter is vertically polarised
4. As the 2nd filter is rotated less light will get through its vertical component so its intensity decreases
5. When the filters are at 45° to each other the intensity will be half, if they are at 90° the intensity is 0
33
Why don’t polarising filters work on microwaves
Their wavelength is too long, so metal grilles are used instead
34
What is the plane in which a wave vibrates called
Plane of polarisation
35
What happens to diffraction if the gap is bigger than the wavelength
The diffraction is unnoticeable
36
When do u get the most diffraction
When the gap is the same size as the wavelength
37
What happens as the gap gets smaller
Diffraction increases until the gap is too small for a wavelength to pass through so the waves are reflected
38
What is an aperture
A gap
39
What is the angle of incidence always equal to
The angle of reflection
40
What is reflection
When a wave is bounced back when it hits a boundary
41
Diffraction def
When a wave spreads out as it passes through an aperture or past an edge
42
When does refraction occur
When a the medium a wave is travelling in changes
43
Does the wave bend towards or away from the normal as it speeds up
Away
44
Does the wave bend towards or away from the normal as it slows down
Towards
45
Why does the speed change when entering a differently optically dense material
The wavelength changes and the frequency stays constant
46
Investigating refraction
1. Place a … block on a piece of paper and … around it
2. Use a … box and shine a … of light into the block
3. Trace the … and outgoing beams of light either side of the block
4. … the block and join up the 2 … with a … line
5. Measure the angles of …. and …. where the light enters and … the block
1. Place a glass block on a piece of paper and trace around it
2. Use a ray box and shine a beam of light into the block
3. Trace the incoming and outgoing beams of light either side of the block
4. Remove the block and join up the 2 paths with a straight line
5. Measure the angles of incidence and refraction where the light enters and exits the block
47
What does refractive index show
How much a material slows down light
48
Equation linking n, c, v
C=nv
49
What is the speed of light in a vacuum
3 x 10 ⁸ ms-1
50
Snells law
n₁sin(θ₁) = n₂sin(θ₂)
n is the refractive index
51
What happens as u increase the angle of incidence to the angle of refraction
The angle of refraction gets closer to 90°
52
What happens to the light when the angle of refraction is 90°
The light is refracted along the boundary
53
What happens at angles of incidence greater that the critical angle
All the light is reflected back into the material
54
What is total internal reflection
When the angle of incidence is greater than the critical angle all the light is reflected back into the material
55
What is the critical angle
Maximum angle of incidence before total internal reflection occurs
56
Equation for light hitting a material to air boundary
sin C = 1/n
C = critical angle
n = refractive index
57
What is the principle of superposition
When 2 waves of the same type overlap, they superpose and their displacements add together to produce a single resultant displacement
58
Amplitude
Maximum displacement point of a point on a wave from its equilibrium position
59
What happens if 2 progressive waves interact continuously
They superpose to produce an interference pattern
60
What happens if waves arrive in phase
Constructive interference happens
61
What happens if waves arrive in antiphase
Destructive interference
62
Refractive index
Ratio of speed of light in a vacuum to the speed of light in a medium
63
What does it mean if waves are coherent
They have a constant wave difference, only possible if they have the same frequency
64
What is interference
When 2 or more waves superpose
65
What does a crest plus a crest produce
A bigger crest
66
What does a crest and trough of equal size give
Nothing, the displacements cancel each other out
- this is destructive interference
67
When are 2 points in a wave in phase
When they are at the same point on a wave cycle
68
What number shows 1 complete wave
360° or 2𝜋 radians
69
2 points with a phase difference of 0 or a multiple of 360° are in …
Phase
70
2 points with a phase difference of odd number multiples of 180° (𝜋 radians) are in …
Anti phase
71
What is needed to get clear interference patters
The sources must be coherent
72
When are 2 sources coherent
When they have the same wavelength and frequency with a fixed phase difference
73
Path difference
Difference between the distances travelled by each wave from the source, measured in multiples of λ
74
If the path difference is nλ what type of interference occurs
Constructive
75
If the path difference is λ(n+1/2) what type of interferes occurs
Destructive
76
When do patterns of maxima and minima appear
Due to positions of high intensity, from constructive interference, and positions of low intensity, from destructive interference
77
What is the path and phase difference at central maxima
0
78
Order of path and phase difference
2nd order maxima
2nd order minima
1st order maxima
1st order minima
Central maxima
…
79
Path and phase difference at:
2nd order maxima
2nd order minima
1st order maxima
1st order minima
Central maxima
2 λ. 4 𝜋
3/2 λ. 3 𝜋
λ. 2 𝜋
1/2 λ 𝜋
0. 0
…
80
What is a maxima
A position on a stable interference pattern of maximum intensity due to constructive interference
81
What is a minima
A position on a stable interference pattern of minimum intensity due to destructive interference
82
When does a bright fringe occur
When waves from both slits interfere and are in phase
83
What happens when radio waves are polarised by a grill, filter is vertical
1. The horizontal components of the unpolarised wave are absorbed by the grill
2. The vertical components are not absorbed so carry on creating a vertically polarised wave
83
What is meant by unpolarised light
Electric field oscillates in every plane perpendicular to direction of travel
83
how does diffraction lead to maximas and minimas
-… waves … on a screen
-minimas appear when waves are in … due to … interference when there are … wavelengths
-maximas appear when waves are in … due to … interference when there are … wavelengths
-Coherent waves superpose on a screen
-minimas appear when waves are in antiphase due to destructive interference when there are half wavelengths
-maximas appear when waves are in phase due to constructive interference when there are full wavelengths
84
What components of a wave do not change when a wave is reflected
Frequency, wavelength and speed
85
What components change and stay the same when a wave is refracted
Stays the same:
Frequency
Changes:
Wavelength
Speed
86
What changes and what stays the same during diffraction
Same:
Wavelength
Frequency
Speed
Changes:
Amplitude
Intensity
87
What unit does refractive index have
No unit
88
What is the smallest possible value for reflective index
1- vacuum
89
Difference between energy in stationary and progressive waves
Stationary: store energy on itself
Progressive: transport energy from one place to another
90
Which type of wave doesn’t have permanent maxima or minimas
Progressive waves
91
When does a stationary wave form
When 2 progressive waves of the same frequency travel in opposite directions and superpose
92
What is a node
A point on a stationary wave where the displacement is 0
93
What is an antinode
A point on a stationary wave where the displacement is at its maximum
94
What are any 2 points either side of a node in
Antiphase
95
What are 2 points between adjacent nodes in
Phase
96
Difference between amplitude on a stationary and progressive wave
Progressive: all parts of the wave have the same amplitude
Stationary: maximum amplitude occurs at the antinode
97
Wavelength or stationary waves vs progressive waves
Progressive: minimum distance between 2 adjacent points that are oscillating in phase eg. 2 peaks
Stationary: twice the distance between adjacent nodes/ antinodes
98
Forumla linking x, a, λ, D
x = λD/a
x= fringe spacing
λ= wavelength
D= distance from slits to screen
a= space between slits
99
What is the fundamental frequency
The minimum frequency of a stationary wave for a string
100
What is the 1st harmonic
The lowest frequency that will produce a standing wave
101
For a stationary wave what is the wavelength
Fundamental:
2nd harmonic:
3rd harmonic:
4th harmonic:
Fundamental: 2L
2nd harmonic: L
3rd harmonic: 2L/3
4th harmonic 2L/4
5th harmonic 2L/5
102
For a stationary wave what is the frequency
Fundamental: f₀
2nd harmonic: 2f₀
3rd harmonic: 3f₀
4th harmonic: 4f₀
5th harmonic: 5f₀
103
How much of a wavelength is a node to a node
Half
104
How much of a wavelength is a node-node-node-node
3/2
105
What forms at a closed end of an instrument
A node
106
Equation linking k, v, T
v= k square root T
k= constant
t= tension
107
Does the frequency and wavelength change for opened and closed tubes
No
108
What forms at open ends of instruments
Antinodes
109
What is the wavelength for waves fixed at one end
Fundamental: 4L
3rd harmonic: 4L/3
5th harmonic: 4L/5
7th harmonic: 4L/7
110
What is special about harmonics for waves fixed at one end
The harmonic cannot be even, as it would be closed at both ends
111
Frequency for waves fixed at one end (harmonics)
Fundamental: f₀
3rd harmonic: 3f₀
5th harmonic: 5f₀
7th harmonic: 7f₀
112
When does total internal reflection happen
-angle of incidence is bigger than the critical angle
113
What is the displacement of 2 waves with destructive interference
0
114
Coherence def
When 2 waves have a constant phase difference
Alevel physics
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