Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics Yr1 > Diffraction > Flashcards

Diffraction Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

Define Path Difference

A

The difference in the distance travelled by 2 waves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a coherent source of waves

A

Source that emits light waves with constant path difference and the same frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Monochromatic Light

A

A Light Wave that is formed of 1 wavelength of light It shows interference the clearest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is Young’s Double Slit Experiment (YDSE)

A

Shine monochromatic light from 2 coherent sources with equal width so it diffracts, forming a pattern of light and dark fringes on a screen.

Due to the superposition of waves at the screen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

In YDSE, when is a Bright Fringe formed

A

When 2 light waves meet in phase and superpose Constructive interference occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

In YDSE, when is a Dark Fringe formed

A

When 2 light waves meet completely out of phase and superpose

Destructive interference occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the equation used to calculate the fringe spacing of the pattern formed in young’s double slit experiment

A

(Wavelength x Dist.) / Slit Seperation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When does destructive interference occur

A

When one wave has positive displacement and the other has negative displacement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

When does constructive interference occur

A

When 2 waves have displacement in the same direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What pattern will be produced when white light is used in YDSE

A

A wider maxima and less intense pattern

Central fringe will be white

Each component colour of white will diffract differently to produce its own fringe pattern which mixes with other fringe patterns

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How can one use sound waves for YDSE

A

Use 2 speakers from the same isgnal genertor so the wave is coherent Use microphone to find intensity of wave to get maximas/minimas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is Diffraction

A

Spreading out of waves when they pass through a gap or around an obstacle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does diffraction vary with the size of the gap

A

Diffraction is greatest when the gap is the same size as the wavelength

When the gap is smaller, more reflection will occur When the gap is bigger, less diffraction will occur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens when monochromatic light is diffracted through a single slit onto a screen

A

Interference pattern is produced as the wave ‘interferes with itself’ due to Huygens principle

There is a bright central fringe that is double the width of the other fringes Intensity of the fringes decreases the further out from the central fringe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is a diffraction grating

A

A slide containing many equally spaced slits very close together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What kind of interference pattern is produced when monochromatic light is shone through a diffraction grating

A

A brighter, sharper pattern

As there are more slits, more rays interfere with each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is X-ray crystallography

A

Shine an X-ray through a thin crystal sheet since the dist. between atoms is similar to the wavelength of an X-ray Acts as a diffraction grating, forming a pattern that can be used to find atomic spacing in material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Define Refraction

A

The change of direction that occurs when light passes at an angle across a boundary between 2 transparent substances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which way does light refract going into a more dense material

A

Towards the normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which way does light refract going into a less dense material

A

Away from the normal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is Snells law

A

sin i/sin r = Refractive Index

is a property of a material, any light ray passing through the same material will have the same refractive index

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is Refractive Index

A

A measure of optical density

As the angle by which light is refracted is determined by how much the particles in the wave front slow down A more optically dense material will slow down particles more and have a higher refractive index

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is absolute Refractive Index

A

Ratio between the speed of light in a vacuum and the speed of light in the material n=3x10^8 / speed of light in material

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is relative Refractive Index

A

Ratio of the speed of light between materials sin x(1) / sin x (2) = n(2) / n(1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

When does Total Internal Reflection occur

A

When angle i is greater than the critical angle

26
Q

What is the critical angle

A

The angle of i when its refracted ray travels along the boundary So angle of refraction is 90

27
Q

What is the symbol for a Thermistor

A
28
Q

What kind of interference pattern is produced when monochromatic light is diffracted through a single slit onto a screen

A

There is a bright central fringe that is double the width of the others.

Intensity decreases the further out from the central fringe

29
Q

Equation for the interference pattern produced when monochromatic light is shone through a diffraction grating

A

dsin (x) = n x Wavelength

n = No. Order

x - Angle to 0 order line

d - Dist. between slits

30
Q

Equation to use for any refraction question

A

n(1)sin (x(1)) = n(2)sin(x(2))

n(1) - refractive index of first material

x(1) - angle of incidence

31
Q

Define Amplitude

A

A wave’s maximum displacement from the equilibrium position

32
Q

Define Frequency

A

The number of complete oscillations passing through a point per second

33
Q

Define Wavelength

A

The length of one whole oscillation (e.g. the distance between successive peaks/troughs)

34
Q

Define Phase Difference

A

How much a particle/wave lags behind another particle/wave

35
Q

Define Period

A

Time taken for one full oscillation

36
Q

What is a progressive wave

A

A wave that transfers energy without transferring material

Made up of particles of a medium oscillating

37
Q

Define a transverse wave

A

Wave where the oscillation of particles is at right angles to the direction of energy transfer

38
Q

Define a longitudinal wave

A

A wave where the oscillation of particles is parallel to the direction of energy transfer

These are made up of compressions and rarefactions and can’t travel in a vacuum.

39
Q

What is a polarised wave

A

A wave that only oscillates in one plane

40
Q

What does a polarised wave provide evidence for

A

True nature of a transverse wave

Only transverse waves can be polarised as particles oscillate perpendicular to the direction of travel

41
Q

How do polaroid sunglasses work

A

Sunlight gets partially reflected on water, roads, shiny surfaces and all the wavelengths therefore line up into one very intense line of polarised light, usually in a horizontal plane

The sunglasses have a filter that polarizes this light, only letting in light in the vertical plane, which is much less intense

42
Q

How is polaristation used in TV/radio signals

A

Signals are plane polarised by the orientation of the transmitting ariel

So the receiving aerial must be aligned in the same plane of polarisation to receive the signal at full strength.

43
Q

What is superposition

A

Where the displacements of two waves are combined as they pass each other, the resultant displacement is the vector sum of each wave’s displacement

44
Q

How is a stationary wave formed

A

From the superposition of 2 progressive waves, travelling in opposite directions in the same plane, with the same frequency, wavelength and amplitude.

45
Q

What is an antinode, how are they formed

A

Point of maximum amplitude on a stationary wave

Waves meet in phase and constructive interference occurs

46
Q

What is a node, when is it formed

A

Point of no displacement on a stationary wave

Waves meet completely out of phase, total destructive interference occurs

47
Q

What is the first harmonic

A

The lowest frequency at which a stationary wave forms

2 nodes and an antinode

48
Q

How are stationary microwaves formed

A

By reflecting a microwave beam at a metal plate,

Use a microwave probe to find nodes/antinodes

49
Q

How are stationary sound waves formed

A

By placing a speaker at one end of a closed glass tube, lay powder across the bottom of the tube.

It will be shaken at the antinodes and settle at the nodes.

50
Q

Name I use of Total Internal Reflection

A

Optical fibres

51
Q

What is an optical fibre, how do they work

A

Flexible, thin tubes of plastic or glass which carry information in the form of light signals.

They have an optically dense core surrounded by cladding with a lower optical density to:

Allow TIR to occur

Protects the core from damage

Prevent signal degradation through light escaping the core, which can cause information to be lost.

52
Q

What can cause signal degradation

A

Absorption

Modal, Material dispersion = Pulse Broadening

53
Q

How is signal degradation caused by Absorption

A

Part of the signal’s energy is absorbed by the fibre, reducing the amplitude of the signal, which could lead to a loss of information

54
Q

How is signal degradation caused by dispersion

A

Pulse broadening

The received signal is broader than the original transmitted signal. Broadened signals can overlap causing loss of information.

55
Q

What is modal dispersion

A

Pulse broadening caused by light rays entering the fibre at different angles, therefore they take different paths along the fibre

This leads to the rays taking a different amount of time to travel along the fibre

56
Q

How can modal dispersion be reduced

A

Making the core very narrow, therefore making the possible difference in path lengths smaller.

Optical fibre repeater - repeats the signal during its travel

57
Q

What is material dispersion

A

Pulse broadening caused by light consisting of different wavelengths, meaning light rays will travel at different speeds along the fibre

58
Q

How can material dispersion be reduced

A

Using monochromatic light

Optical fibre repeater - repeats the signal during its travel

59
Q

How to derive dsin (x) = n x Wavelength

A

Considering the first order maximum, where the path difference between two adjacent rays of light is one wavelength, name the angle between the normal to the grating and the ray of light θ.

As you can see a right angle triangle is formed, with side lengths d and λ. And by using the fact that a right angle is 90°, and angles in a triangle add up to 180°, you can see the upper angle in the triangle is θ.

By using trigonometry we can see that for the first maximum sin θ = , (as sin θ = d λ Opp/Hyp) which rearranges to , (for the first order). dsin θ = λ

We know that the other maxima occur when the path difference between the two rays of light is nλ, where n is an integer, therefore we can generalise the equation by replacing λ with nλ to get:

d sinθ= nλ

60
Q

Name 2 uses of diffraction gratings

A

X-Ray Crystallography

Line Absorption spectra

Physics Yr1 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions