Waves Flashcards
(74 cards)
1
Q
oscillation
A
back and forth motion
2
Q
periodic
A
repetititive oscillation
3
Q
period
A
- time taken to complete one full oscillation
- T
4
Q
amplitude
A
- maximum displacement of an oscillation from its equilibrium position
- A
5
Q
restoring force
A
force that brings the system back to its equilibrium position when the system is displaced away from its equilibrium
6
Q
What is necessary for a system to oscillate?
A
restoring force
7
Q
simple harmonic motion requirements
A
- magnitude of acceleration of body that has been displaced from equilibrium is proportional to the displacement and direction of the acceleration towards the equilibrium
- fixed equilibrium position
8
Q
frequency
A
number of full oscillations per second
9
Q
frequency equation
A
f = 1/T
10
Q
graph showing the variation of displacement, velocity and acceleration in SHM
A
11
Q
phase difference with graph representation
A
amount by which one curve is shifted forward relative to another curve
12
Q
equation for phase difference
A
angle = shift/T x 360degrees
13
Q
graph showing energy in SHM
A
14
Q
wave
A
- disturbance that travels in a medium
- transfers energy and momentum from one place to another
- direction of propagation of wave is direction of energy transfer
- no large-scale motion of the medium itself as the wave passes through
15
Q
superposition
A
when two or more waves of the same type arrive at point in space at same time displacement of medium is sum of individual displacements
16
Q
wavelength
A
length of a complete oscillation
17
Q
- crest
- trough
A
- highest point on the wave
- lowest point on the wave
18
Q
transverse wave
A
displacement perpendicular to direction of energy transfer
19
Q
longitudnal wave
A
displacement parallel to direction of energy transfer
20
Q
- compression
- rarefaction
A
- areas of high pressure
- areas of low pressure
21
Q
Can you tell the difference between transverse and longitudinal waves using a displacement-distance graph?
A
no - both look the same
22
Q
diagram of an electromagnetic wave
- wavelength
- magnetic field
- electric field
A
23
Q
At what speed do electromagnetic waves propagate in a vacuum?
A
speed of light
24
Q
are electromagnetic waves longitudinal or transverse?
A
transverse
25
wavefronts
* surface through crests
* normal to direction of energy transfer
26
rays
* lines perpendicular to wavefronts
* show direction of wave propagation and energy transfer
27
What is the phase difference of wavefronts?
all points on wavefront have zero phase difference
28
diagram of wavefronts
1. ray
2. wavefronts
3. wavelength
29
How are pulses reflected?
1. On a fixed end
2. On a loose end
1. pulse exerts equal and opposite force on fixed end, so pulse is inverted when reflected
2. reflected pulse not inverted because free to move
30
plane polarised
when electric field oscillates on the same plane
31
polarisation with diagram
light is transmitted through certain media so all vibrations are limited to a single plane
32
polariser with diagram
sheet of material with a molecular structure that only allows a specific orientation of the electric field to go through
33
How to resolve components in a polariser?
vertical polarizer so only vertical component of electric field will go through
34
What happens when horizontal and vertical polarizers are at right angles?
crossed polarisers transmit no light so when overlap appear black
35
What happens when unpolarised light reflects off a non-metallic surface?
partially polarised - produces glare (horizontally polarised)
36
law of reflection and diagram
* angle of incidence is equal to angle of reflection
* reflected and incident rays and normal lie on same plane (plane of incidence)
37
Requirements for reflection to take place
* reflecting surface must be sufficiently smooth
* wavelength of incidence wave must be larger than size of irregularities on surface (=wavelength of reflected waves)
38
refraction and diagram
travel of light from one medium to another where it has a different speed
changes direction of incident ray unless normal to boundary of media
39
Snell's law for light
n1sinO2 = n2sinO1
40
refractive index equation
nm = c/cm
where nm is the refractive index of a medium
41
dispersion
rays with the same angle of incidence but of different wavelength are refracted by different angles
42
What causes white light to split up when passed through a prism?
dispersion of different wavelengths of light
43
How does the wavelength, frequency and speed of a wave change when it passes to another medium?
* frequency remains the same
* speed changes (increases as wavelength increases)
* wavelength changes (increases as speed increases)
44
How does the wavelength affect the diffraction of a wave? Diagram
if wavelength small compared to gap: little diffraction
if wavelength large compared to gap: a lot of diffraction
45
critical angle
angle of incidence for which the angle of refraction is 90 degrees
46
total internal reflection with diagram
* occurs when angle of incidence is greater than the critical angle
* no refracted ray; just the reflected ray
47
diffraction
spreading of a wave as it goes past an obstacle or through an aperture
48
diagrams for diffraction around obstacle and edge
49
double slit interference diagram
bright spots marked as n - indicates that path difference is n\*wavelength
dark spots indicate that path difference is 1/2n\*wavelength
50
fringe spacing
* distance on double slit screen between the middle of the bright spot and the middle of the next bright spot
* symbol is s
51
Which light has larger fringe spacing, red or green?
red because has longest wavelength
52
standing (stationary) wave
wave in which the crests stay in the same place
53
How is a standing wave formed?
when two waves of the same speed, wavelength and amplitude travelling in opposite directions meet
54
What is the displacement of a standing wave compared to the original travelling waves?
sum of displacements of two travelling waves
55
node
place on a wave where the displacement is always zero
56
What is the wavelength of a standing wave?
distance between two consecutive nodes
57
antinode
point where displacement of a standing wave is as large as possible
58
Where are standing waves in phase?
points between consecutive waves
59
What are the differences between standing waves and travelling waves?
* standing waves do not transfer energy; travelling waves do
* the amplitude of oscillation is different at different points on the standing wave; same on travelling wave
* all points between two successive nodes on a standing wave are in phase; two neighbouring points on a travelling wave not in phase
60
first harmonic
standing wave with longest wavelength and lowest frequency
61
diagram showing patterns of increasing harmonics
1. wavelength
2. frequency
1. decreases with increasing harmonic
2. increases with increasing harmonic
62
how do molecules move in a longitudinal standing wave in a pipe with antinode-antinode? diagram for first and second harmonics
* molecules oscillate most at the ends (antinodes)
* molecules do not oscillate in the middle (node)
63
What is the first harmonic also called?
fundamental frequency (has lowest frequency)
64
how to molecules move in a longitudinal standing wave in a node-node pipe? diagram for first and second harmonics
65
how to molecules move in a longitudinal standing wave in a node-antinode pipe? diagram for first and second harmonics
66
What type of wave is a standing wave in a tube?
longitudinal wave
67
What is the wavelength of a standing wave?
68
Intensity graph for single slit diffraction
69
Intensity graph for double slit diffraction
70
Effect on single slit diffraction pattern:
1. if the width of the slit is reduced?
2. if a red light source is replace with a green light source?
1. Wider diffraction pattern; dimmer
2. green light has smaller wavelength so narrower diffraction pattern with brighter central spot
71
72
Effect on double slit diffraction pattern if one narrow slit covered by opaque object?
* large central fringe
* side fringes narrower than central fringe
* single slit diffraction pattern
73
coherent source
source whose phase difference is constant in time and whose waves have the same frequency
74
Why should single slit be narrow in single slit diffraction?
ensure wide diffraction
