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AS Physics > G482 - Waves > Flashcards

G482 - Waves Flashcards

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0
Q

Progressive Wave

Definition

A

A transfer of energy as a result of oscillations

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1
Q

Longitudinal Wave

Definition

A

A wave in which the oscillations are parallel to the direction of wave travel

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2
Q

Transverse Wave

Definition

A

A wave in which the oscillations are perpendicular to the direction of wave travel

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3
Q

Longitudinal Wave

Examples

A

Sound

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4
Q

Transverse Wave

Examples

A

Light
Water
String

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5
Q

Displacement

Definition

A

The distance of a particle from the equilibrium position

Measured in metres, m

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6
Q

Amplitude

Definition

A

Maximum displacement of a particle from equilibrium
Symbol A
Measured in metres, m

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7
Q

Wavelength

Definition

A

The shortest distance between a point on one wave and the same point on the next wave
Symbol λ
Measured in metres, m

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8
Q

Time Period

Definition

A

The time taken for one complete pattern of oscillation
Symbol T
Measured in seconds, s

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9
Q

Phase Difference

Definition

A

Relates to the oscillation at two points
How far out of step one oscillation is from another
Measured in degrees or radians

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10
Q

Frequency

Definition

A

The number of oscillations per unit time
Symbol f
Measured in hertz, Hz

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11
Q

Wave Speed

Definiton

A

Distance travelled by a wave per unit time

Measured in m/s

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12
Q

Time Period

Formula

A

T = 1/f

T = time period, s
f = frequency, Hz
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13
Q

Wave Speed

Formula

A

v = fλ

v = wave speed, m/s
f = frequency, Hz
λ = wavelength, m
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14
Q

Reflection

Definition

A

When waves rebound from a barrier changing direction but remaining in the same medium

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15
Q

Diffraction

Definition

A

When a wave spreads out after passing around an obstacle or through a gap
When the gap is closer in size to the wavelength of the wave there is more diffraction
Diffraction around an obstacle increases with wavelength

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16
Q

Refraction

Definition

A

When waves change direction when they travel from one medium to another due to a difference in the wave speed in each medium

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17
Q

Typical Wavelengths

Radio Waves

A

10^-1 -> 10^4 m

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18
Q

Typical Wavelengths

Microwaves

A

10^-4 -> 10^-1 m

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19
Q

Typical Wavelengths

Infrared

A

7.4x10^-7 -> 10^-3 m

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20
Q

Typical Wavelengths

Visible Light

A

3.7x10^-7 -> 7.4x10^-7 m

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21
Q

Typical Wavelengths

Ultraviolet

A

10^-9 -> 3.7x10^-7 m

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22
Q

Typical Wavelengths

X Rays

A

10^-12 -> 10^-7 m

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23
Q

Typical Wavelengths

Gamma

A

10^-16 -> 10^-9 m

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24
Q

Electromagnetic Spectrum Order

A 
Radio Waves
Microwaves
Infrared
Visible Light
Ultraviolet
X Rays
Gamma
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25
Q

Electromagnetic Spectrum

Similarities

A

Travel at the same speed in a vacuum
All transverse waves
All possess an electric wave and a magnetic wave interlocked at right angles

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26
Q

Electromagnetic Waves

Speed in a Vacuum

A

3x10^8 m/s

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27
Q

Speed of Sound In Air

A

330m/s

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28
Q

Radio Waves

Method of Production

A

Electrons oscillated by an electric field

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29
Q

Radio Waves

Method of Detection

A

Resonance in electric circuits

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30
Q

Radio Waves

Uses

A

Television
Radio
Telecommunications

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31
Q

Microwaves

Method of Production

A

Magnetron

Klystron oscillators

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32
Q

Microwaves

Method of Detection

A

Heating effect

Electronic circuits

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33
Q

Microwaves

Uses

A

Radar
SATNAV
Mobile phones
Microwave ovens

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34
Q

Infrared

Method of Production

A

Oscillation of molecules from all objects above absolute 0

35
Q

Infrared

Method of Detection

A

Photographic film

Heating of skin

36
Q

Infrared

Uses

A

Heaters
Night vision equipment
Remote controls

37
Q

Visible Light

Method of Production

A

High temperature solids and gases

Lasers

38
Q

Visible Light

Method of Detection

A

Photographic film

Retina of eye

39
Q

Visible Light

Uses

A

Sight

Communication

40
Q

Ultraviolet

Method of Production

A

From high temperature solids and gases

41
Q

Ultraviolet

Method of Detection

A

Photographic film
Phosphors
Sunburn

42
Q

Ultraviolet

Uses

A

Disco lights
Tanning studios
Counterfeit detection

43
Q

X Rays

Method of Production

A

Bombarding metals with high energy electrons

44
Q

X Rays

Method of Detection

A

Photographic film

Fluorescence

45
Q

X Rays

Uses

A

CT scans
X Ray photography
Crystal structure analysis

46
Q

Gamma Rays

Method of Production

A

Nuclear decay

In a nuclear accelerator

47
Q

Gamma Rays

Method of Detection

A

Photographic film

Geiger tube

48
Q

Gamma Rays

Uses

A

Diagnosis and cancer treatment

49
Q

UV-A

A

λ = 315 - 400 nm

Causes tanning when skin is exposed

50
Q

UV-B

A

280-315nm

Causes damage to skin such as sun burn and skin cancer

51
Q

UV-C

A

100-280nm
Is filtered out by the atmosphere so doesn’t reach the earth’s surface
Industrial UV-C is highly damaging

52
Q

Sunscreen

A

Contains chemicals designed to filter out UV-B pre eating sun burn and skin cancer
Skin is protected inside as glass absorbs UV-B

53
Q

Plane Polarised Waves

Definition

A

Waves that oscillate in only one plane

Only transverse waves can be pale polarised

54
Q

Malus’s Law

A

I = Imax x cos²θ

I = intensity transmitted at angle θ
Imax = intensity before the filter 
θ = the angle of the filter in relation to the previous filter that the light has travelled through
55
Q

Cross Polaroids

A

If filters are at right angles, θ=90, then no light will pass through

56
Q

The Principle of Superposition

A

When two or more waves meet at a point the resultant displacement is equal to the vector sum of the displacements of each wave

57
Q

Interference

Definition

A

The addition of two or more waves that results in a new wave pattern
Sources must be coherent
Amplitude must be approximately equal

58
Q

Coherence

Definition

A

Two waves are coherent if they have a constant phase difference and the same frequency

59
Q

Path Difference

Definition

A

Distance between two identical points on the two waves

Measured in λ

60
Q

Constructive Interference

Path Difference

A

Whole number of wavelengths

61
Q

Constructive Interference

Phase Difference

A

0°, 360°, 720°… multiples of 360°

0, 2π, 4π radians … multiples of 2π

62
Q

Destructive Interference

Path Difference

A

Odd number of half wavelengths

63
Q

Destructive Interference

Phase Difference

A

180°, 540°, 900°… multiples of 2n(180)+180

π, 3π, 5π radians… multiples 2nπ +1

64
Q

Intensity

Formula

A

Intensity(W/m²) = Power W / cross sectional area m²

Intensity∝Amplitude²

65
Q

Intensity

Definition

A

Energy incident per unit area per unit time

66
Q

Young’s Double Slit Experiment

Description

A

A monochromatic light source is positioned between two slits
When the light passes through the slits it is diffracted
The two light sources, the two slits, interferes with each other to produce an interference pattern
The pattern consists of a series of maxima and minima
At minima the path difference is an odd number of half wavelengths so there is destructive interference
At maxima the path difference is a whole number of wavelengths so there is constructive interference

67
Q

Young’s Double Slit Experiment

Formula

A

λ = ax/D

λ = wavelength m 
a = distance between slits m
x = distance between bright fringes m
D = distance between slits and screen
68
Q

Monochromatic Light

A

Light waves with a single frequency and wavelength

69
Q

Finding the Wavelength if Monochromatic Light

A 
Use the laser as the source
Carry out young's double slit experiment
Measure a and D
Take an average measurement for x
Use λ=ax/D
70
Q

Diffraction Grating

Formula

A

sinθ = nλ/d

θ = angle of the beam from horizontal
n = order of the beam
λ = wavelength of source
d = spacing between slits
71
Q

Advantages of Multiple Slits

A

Many sharp maxima can be observed so measurements are easier and more accurate
Double slit images can sometimes be blurry increasing error when measuring fringe spacing

72
Q

Stationary Wave

Definition

A

A wave formed by the interference of two waves travelling in opposite directions
Energy is stored in the wave which has nodes and antinodes

73
Q

Nodes

Definition

A

Points in a stationary wave at which the displacement is 0

74
Q

Antinodes

Definition

A

Points in the stationary wave where the displacement is maximum

75
Q

Fundamental Frequency

Definition

A

Frequency that gives a standing wave of half a wavelength

76
Q

Harmonics

Definition

A

Whole number multiples of the fundamental frequency of a stationary wave

77
Q

What is the distance between two nodes or two antinodes?

A

Half a wavelength

78
Q

Wave Patterns
Stretched Strings, Open Pipes, Closed Pipes
nth harmonic

A

Wavelength = Fundamental Wavelength / n

Frequency = Fundamental Frequency x n

79
Q

Wave Patterns
Stretched Strings, Open Pipes, Closed Pipes
fundamental

A

Fundamental Wavelength = 2l

Fundamental Frequency = v/2l

l = length of string or pipe

80
Q

Wave Patterns
Pipes Closed at One End
fundamental

A

Fundamental Wavelength = 4l

Fundamental Frequency = v/4l

l = length of pipe

81
Q

Wave Patterns
Pipes Closed at One End
nth harmonic

A

Wavelength = Fundamental Wavelength / (2n+1)

Frequency = Fundamental Frequency x (2n+1)

82
Q

Stationary Waves

Microwaves

A

Set up a transmitter opposite a reflector with a detector in the middle
The detector will register strong signals every half wavelength i.e. nodes

83
Q

Stationary Waves

Guitars

A

When the string is plucked a transverse wave is sent down the string and reflected
The reflected wave interferes with the incident wave to produce a stationary wave of the correct pitch

84
Q

Experiment to Find the Speed of Sound in Air

A

Put an open ended tube into water to ‘close’ the tube at one end
Sound a tuning fork and hold it close to the tube
The tube is open at one end so there is an antinode, maxima, at the opening
Move the tube up and down in the water to find where the resonance is maximum, where there is λ/4 inside the tube
Measure the distance from the top of the water level to the top of the tube at this point
Multiply this distance by 4 to find the λ
The tuning fork has its frequency written on
Use v=f λ to find v

AS Physics (4 decks)

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