Waves & Particle Nature of Light Flashcards

(105 cards)

1
Q

What is a progressive wave?

A

A progressive wave is a wave that transfers energy but not matter.

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2
Q

What are mechanical waves?

A

Mechanical waves are waves that need a medium to travel through.

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3
Q

What is a transverse wave?

A

A transverse wave is a wave where oscillations are perpendicular to the direction energy transfer (wave direction).

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4
Q

What is a longitudinal wave?

A

A longitudinal wave is a wave where the oscillations are parallel to the direction of energy transfer (wave direction).

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5
Q

What is compression?

A

When particles are tightly packed together.

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6
Q

What is rarefraction?

A

When particles are spread far apart.

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7
Q
  1. What is wavelength (definition)?
  2. What is wavelength in terms of longitudinal waves?
A
  1. Distance between two identical points on two adjacent waves
  2. Distance from one compression to another compression or one rarefraction to another rarefraction.
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8
Q

What is amplitude?

A

Amplitude is the maximum displacement from rest position.

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9
Q

What is frequency?
What are the units for frequency?

A

-Frequency is the number of complete waves passing a point per second.
-The units are Hertz (Hz) or per second (s^-1)

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10
Q

What is Time period?
What are the units for time period?

A

-Time period is the time taken for a full wave cycle
-The units are in seconds (s).

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11
Q

What is the formula for Time period?

A

Frequency = 1/Time period

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12
Q

What is the formula for wavespeed with units?

A

Wavespeed (m/s) = Frequency (Hz or s^-1) X Wavelength (λ)

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13
Q

What is the velocity of an electromagnetic wave?

A

the velocity of an electromagnetic wave is 3 X 10^8 (MEMORISE)

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14
Q

What is the most common unit of measurement of angles?
What is an alternative measurement?

A

Degrees is the most common unit of measurement for angles.
Radians is an alternative measurement for angles?

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15
Q

How do you convert radians to degrees?
How do you convert degrees to radians?

A

-From radians to degrees you multiply by 180 and divide by π (180/π).
-From degrees to radians you multiply by π and divide by 180 (π/180).

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16
Q

What is phase in a waves?

A

Phase in a wave is the fraction of the particle cycle it has completed since the start of the cycle.

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17
Q

What is one wavelength equal to in degrees and radians?

A

Degrees- 360
Radians- 2π
Tip: Every half a wavelength is 180 degrees

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18
Q

In a single wave, when is:
1.The wave in phase?
2. What does that mean in terms of the wave?
3.The wave out of phase?
4. What does that mean in terms of the wave?

A

1.A wave is in phase when two points on a wave are on the same point on the wave cycle.
2. This means they have the same displacement/velocity. This means they have a phase difference of 0 degrees or 360 degrees (2π).
3. A wave is out of phase when two points on a wave are in different points on a wave cycle.
4. This means they have different displacement/velocity.

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19
Q

STATEMENT:
Waves can be drawn as wave diagrams or circle diagrams. Sometimes, they may not match.

https://www.google.com/url?sa=i&url=https%3A%2F%2Fstudymind.co.uk%2Fnotes%2Fpath-difference%2F&psig=AOvVaw0lIUxzYdp0FcUpE78lPVhk&ust=1729430713160000&source=images&cd=vfe&opi=89978449&ved=0CBQQjRxqFwoTCPDn4czFmokDFQAAAAAdAAAAABAE

A
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20
Q

In two or more waves, when is:
1. The wave in phase and explain?
2. The wave out of phase and explain?

A
  1. A wave is in phase when the troughs allign or when the peaks allign. This means the waves have the same velocity/displacement
  2. A wave is out of phase when the troughs and crests do not allign. This means that the waves have a different displacement/velocity.
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21
Q

1.What is antiphase and explain in detail?

A

1.It is when the trough and crests are continually alligned (the trough of one wave and the crest of the other wave allign). The waves have an opposite displacement/velocity

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22
Q

What is phase difference measured in?
What is the formula for phase difference?

A

-Phase difference is measured in (π radians).
Phase difference= distance between points/period X2π

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23
Q

What is a wave profile?

A

Wave profile shows shows the position of particles along the surface at that specific time and can be represented on a displacement-distance graph.

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24
Q

What is path difference?
What is it measured in?

A

Path difference is the difference in distance that two waves or two points have travelled.
-Path difference is measured in the units of wavelength (λ).

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25
What is the formula for path diffeence?
Difference between 2 points/ wavelength X2π
26
What are the characteristics of longitudinal waves and what do they mean?
-Molecular displacement- Particles in the medium are displaced parallel to the direction the wave travels -Pressure variations- Caused by oscillation of particles in the medium.
27
Do electromagnetic waves need a medium to travel?
No
28
What two waves are electromagnetic waves made of? What angles are these two waves are to each other?
- Magnetic field waves and electric field waves -The two waves are perpendicular to each other at 90 degrees. https://www.noaa.gov/jetstream/satellites/electromagnetic-waves
29
What are unpolarised waves? Give examples of unpolarised waves?
-Waves that oscillate in more than one direction. -Examples are Electromagnetic waves and light waves
30
What is polarisation?
-Process of restriction of oscillation where a polarised wave will only oscillate in a single plane.
31
How can you make a unpolarised wave into a polarised wave?
By adding a polarising filter https://www.google.com/imgres?q=polarising%20filter%20waves&imgurl=https%3A%2F%2Fspark.iop.org%2Fsites%2Fdefault%2Ffiles%2Fmedia%2Fimages%2Fpolarisation-of-a-transverse-wave.gif&imgrefurl=https%3A%2F%2Fspark.iop.org%2Fepisode-313-polarisation&docid=GnLnGyoZ60U9NM&tbnid=q1gXW0ZGwT46eM&vet=12ahUKEwiXn-2VjP2JAxU1V0EAHTInMygQM3oECGsQAA..i&w=423&h=190&hcb=2&ved=2ahUKEwiXn-2VjP2JAxU1V0EAHTInMygQM3oECGsQAA
32
Why are transverse waves able to be plane polarised?
Because they have a horizontal and vertical component (oscillates in more than one plane).
33
Why can't longitudinal waves be polarised?
They oscillate in one plane only.
34
What happens when an electromagnetic waves passes through a polarising filter?
- The waves will be polarised -The intensity of the waves will be reduced as some waves are stopped.
35
How are radio and television signals broadcasted?
They are either horizontally polarised or vertically polarised so they have to be either mounted horizontally (flat) or vertically (on it's side)
36
What does the polarising filters on the lens of polarised glasses allow them to do?
It only allows vertically polarised light in and not horizontally polarised light in so no glare.
37
What does polarised cameras allow them to do and how do they do it?
Polarised cameras work in the same way as polaroid glasses (doesn't allow horizontal light in) and allows the person to capture intensified colour in the pictures and reduce glare on sunny days.
38
What happens when light is reflected from reflective surfaces?
The light undergoes partial plane polarisation and glare is reduced.
39
How can light be polarised apart from using polarising filter?
-Reflection -Reffraction -Diffraction
40
How can photographers using polarised cameras that have polarising filters allow them to take better pictures underwater?
They can take better pictures as light reflected on the surface is partially polarised in the horizontal plane and the glare is eliminated by the polarising lens. However, light form an underwater object is refracted (not reflected). This means light from underwater object is more intense than the glare and shows up brighter in the photo.
41
What is the principle of superposition?
When two or more waves cross a point and the displacement at that point is equal to the sum of the displacements of the individual waves.
42
What are the 2 conditions in which superposition of waves can happen?
-When the two sources of waves are same type ( e.g. both electromagnetic) -The two waves have to be coherent
43
When are two sources of waves coherent?
Two sources of waves are coherent when they have the same frequency and maintain a constant phase difference (in phase).
44
Why is light from the sun or light bulb not coherent?
This is because light shines in different directions and has a different wavelengths (different colours).
45
How do you make white light coherent?
- Put a coloured filter so that only one colour shows (because white light gives out all colours of light) and it becomes incoherent monochromatic light. - Add single-slit to make a tiny part in phase to make it coherent monochromatic light
46
What is a constructive wave?
When two in phase waves meet and are travelling in the same direction, their displacements combine to make a bigger one. They must be the same type of wave.
47
What is destructive interference?
When a wave with a positive displacement meets one with a negative displacement, they cancel each other out. They must be the same type of waves.
48
- How can we see interference patterns? - Which interference causes bright regions? - Which interference causes darker regions?
- We can see interference patterns using light waves. - Constructive interference causes brighter regions. - Destructive interference causes darker regions.
49
- How can we hear interference patterns? - Which interference causes quieter sounds? - Which interference causes louder sounds?
- We can hear interference patterns using sound waves. - Destructive interference causes quieter sounds. - Constructuve interference causes louder sounds.
50
What is path difference?
Path difference is the difference from each source to a particular point. (Measured in wavelengths).
51
What happens when light passes throught two slits?
when light passes through two slits it diffracts through both of them and interference is created between the two sets of diffracted waves
52
What did Young notice when he conducted the Young's double slit experiment?
He noticed that there wasn't bright regions corresponding to the slits but instead saw bright or dark fringes
53
What and when did Christiaan Hughes present? Why was it rejected?
Hughes presented the wave nature of light. - It was rejected for Issac Newtons corpuscular theory of light ( light being made by tiny particles called corpuscles) because of Newton's reputation untiil when Young demonstrated interference of light.
54
What was the results of Young's double slit experiment?
Dark fringes are fromed when light meets completely ouot of phase and interferes destructively. Bright fringes are formed when the light meets in phase and interferes constructively.
55
What are the conditions for stable interference?
- Waves must be coherent and monochromatic - Waves that have constructive interference have a path difference of nλ. - Waves that destructivel interfere have a path difference of (n+1/2)λ.
56
What is the order of interference?
Number of complete wavelength cycles that fit into the path difference of two waves.
57
What happens when waves are at zero order (n=0)?
It is when waves constructively interfere perfectly
58
The smaller the order of interference the _______ the fringe?
The smaller the order of interference, the brighter the fringe.
59
What is the formula for fringe width?
w= λD/s D= Distance between slit and screen s= Distanfce between two slits
60
What is diffraction?
Diffraction is the spreading out of waves as they pass through a gap.
61
- What does the amount of diffraction depend on? - When does small diffraction occur? - When does a lot of diffraction occur?
- The amount of diffraction depends on the width of the slit compared to the wavelength of the wave. - Small diffraction occurs when wavelength is smaller and slit size is bigger. - Bigger diffraction happens when wavelength is bigger and slit size is smaller.
62
How wide is the central fringe?
Twice as wide as the outer fringes
63
What is a diffraction grating?
Plate with many closely packed slits. You can't see then as there thousands packed together and very small.
64
What is good about having hundred of slits in diffraction gratings?
Becuase of lots of slits, light diffracts better than prisms
65
Why does monochromatic light passing through a diffraction grating travel in a certain direction?
Monochromatic light directed at diffraction gratings travel in a certain direction as light passing through each slit is diffracted so diffracted light from adjacent slits reinforce and cancel each ohter out in certain directions.
66
What is produced on the screen when monochromatic light passes through diffraction gratings?
Patterns of bright narrow fringes are produced on the screen when monochromatic light passes through diffraction gratings.
67
What is the formula for grating spacing (spacing between slits)?
Grating spacing = 1/Lines per metre (not millimetre) d= 1/N
68
What is the general units for diffraction gratings?
Lines per millimetre
69
What is the formula for wavlength of light from diffraction grating?
dsin(θ)=nλ d= grating spacing (between slits) , n= order of maxima
70
For individual drops, what are wave fronts and what do they show?
Wave fronts are concentric circles and the circles show the peaks of the wave.
71
What is Huygen's principle?
Each point on a wave is considered to be a point source of secondary wavelets that spread out in the forward direction at the speed of the wave.
72
When was Huygens principle made?
1690
73
What type of slit and wavelength will cause straighter waves and why?
Bigger slits will and smaller wavelengths will cause straighter waves as diffraction is less.
74
What is a wavefront?
Line/surface joining points on a wave that are in phase.
75
How are standing waves produced?
Interference of two waves of the same frequency and amplitude travelling in opposite directions
76
Give a common example of how standing waves are produced?
It is usually achieved by travellign waves and their reflections.
77
What does the superposition of standing waves make them appear like and what that mean in terms of energy?
The interference of waves make the peak and troughs to look like they aren't moving. Since they don't look like they are moving, they don't transfer energy (like progressive waves) but store it.
78
What happens when a standing waves hits a reflective surface?
It is reflected by 180 degrees but still travels in its original direction.
79
- When are nodes and antinodes formed? - What are nodes? - What are antinodes?
-Nodes and antinodes are formed when there is interference between two standing waves. -Nodes are points of destructive interference when displacement is 0. - Antinodes are points of constructive interference when displacement is maximum.
80
What happens in any other frequency other than harmonic frequency?
Sound sounds unpleasant.
81
What is the harmonic equation?
f= v/2L (Every nth harmonic, you times v by n) f=harmonic, v=wavespeed, L=wavelength in metres (make λ=nL)
82
What is overtone?
Frequencies above fundemental frequencies.
83
What are harmonics?
Overtones that have whole number multiples of the fundemental frequency.
84
What types of waves are harmonics?
Standing waves
85
What type of wave has a frequency that is fundemental frequency?
A wave with 2 fixed ends and has 2 nodes, 1 antinodes.
86
What happens when you increase the amount of energy put in a string?
More waves are created so more nodes and antinodes and different frequency.
87
What does the number of fundementa frequency (f0) depend on?
The number of fundemental frequency depends on the number of half wavelengths (e.g. f3, f5)
88
How can you change the note of a string on an instrument?
You can change the note of the string by: - Chnaging the tension of the string (turn the string) - Thickness of string - Length of string
89
How is the pitch affected by the tension and length of a string?
By rasing the tension and shortening the length of the string, it increases the pitch. By, lowering the tension and extending the length of the string, decreases the pitch.
90
When is a vibrating string considered to be "in tune"?
When its first harmonic frequency is the same as the tuning force frequency.
91
What is the formula for the velocity of a standing wave?
v= √T/u (all square root) T= Tension, u= Mass per length
92
What is the difference between L and λ?
λ is measured in wavlengths L is measured im metres
93
What is the formula for frequency?
f=1/2 X L X √T/u L= wavlength in metres, T= Tension, u=mass per unit length
94
- What is the order of the electromagnetic spectrum? - What is the order of wavelength? - What is the wavelength of frequency?
-Radiowaves, Microwaves, Infrared, Visible light, Ultraviolet, X-Ray, Gamma Rays - High to low wavelengths - Low to high frequency
95
What is the intensity of a wave?
Intensity of a wave is the power (energy passing) per unit area.
96
What is the formula for intensity?
I =P/A P= Power, A= Area
97
What is the area a wave passes through perpendicular to?
Area wave passes through is perpendicular to direction of its velocity.
98
What is a spherical wave?
Wave from a point source that spreads out equally in all directions.
99
What is the formula for the area of a sphere (3D))?
4πr²
100
What is the formula for the area of a circle (2D)?
πr²
101
How does larger diffraction affect waves passing through a slit?
It makes them straighter
102
What does monochromatic frequency mean?
Light with single frequency
103
What does it mean when power is positive? What does it mean when power is negative?
- Converging lens - Diverging lens
104
What happnes when waves pass through a polarising filter?
They are polarised and their intensity is reduced.
105
What types of waves can be polairsed?
Longitudinal not transverse