Brainscape's Knowledge GenomeTM

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


See full index

A-level Physics > Waves And Vibrations > Flashcards

Waves And Vibrations Flashcards

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

What are the two pairs of wave types?

A

Mechanical waves and EM waves.
Transverse and Longitudinal.

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

Define longitudinal waves.

A

When the oscillations are parallel to the propagation of the wave.

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

Define Transverse wave.

A

When the oscillations are perpendicular to the propagation of the wave.

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

What are mechanical waves?

A

Waves that travel through a medium:
Sound waves
Water waves
Seismic waves

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

How do you calculate the period of a wave?

A

Period(s) = 1 / frequency

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

What is polarisation?

A

The polarisation of a wave is the process of making the wave oscillate in only one plane.

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

Which type of waves can be polarised?

A

Transverse waves can be polarised but longitudinal waves can’t as they are not perpendicular to the motion.

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

What are some uses of polarisation?

A

Sunglasses
Liquid Crystal Displays
Radio Waves

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

How do “polaroid” sunglasses work?

A

Light from the OG source is most likely unpolarised. But, annoying reflections are likely to be vertically polarised and can be removed by horizontally polarised lenses.

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

How do you calculate phase difference?

A

2πd / λ

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

How far out of phase is a wave if it is in anti phase compared to the other wave?

A

There is a phase difference of:
πradians or 180°

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

What does a displacement-distance graph show?

A

The displacement from equilibrium along the length of the wave.

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

What does a displacement-time graph show?

A

The displacement of ONE particle at various times.

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

What is displacement?

A

The distance of a particle from equilibrium.

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

What is refractive index?

A

The measure of bending of a ray of light when passing from one medium to another.

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

What is diffraction?

A

The process of waves spreading out after passing through an opening.

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

What factors affect diffraction?

A

Wavelength (longer = more diffraction)
Size of opening ( larger = less diffraction)

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

How does the hardness of a boundary affect reflection?

A

The harder the surface the stronger the reflection.

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

What is total internal reflection?

A

When the angle of incidence exceeds the critical angle the light ray reflects back off of one medium and into the medium it is in. This can only occur when the reflecting medium is less refractive than the current medium.

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

What is the critical angle?

A

The greatest angle a ray of light can strike another medium without TIR occurring.

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

What is Spectral (material) Dispersion?

A

When white light (of different wavelengths) is used in the fibre. Longer wavelengths travel faster than shorter ones in fibre causing distorted results.

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

What is multipath (modal) dispersion?

A

The wider the core of a fibre optic wire, the larger the difference between the light travelling directly along the axis of the fibre and the light repeatedly being internally reflected. This can cause distortion.

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

What are some benefits of fibre optics?

A

Immune to EM interference.
No corrosion.
Higher bandwidth.
No electric current so no heating effect.

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

What are some uses of TIR?

A

Fibre optic communication.
Medical endoscopy.

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

What is the principle of superposition?

A

When two or more waves meet at a point, the resultant displacement is equal to the algebraic sum of the displacement of the individual waves.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is interference?

A

When two or more separate waves combine when passing through each-other producing a resultant wave.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are the two types of interference?

A

Destructive and Constructive.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is constructive interference?

A

When the DISPLACEMENTS of the two waves is in the same direction. This means the resultant wave will have an overall displacement greater than the displacement of either individual wave.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is destructive interference?

A

When the DISPLACEMENTS of the two waves are in opposite directions. This means the resultant wave’s displacement will be less than either individual waves’ displacement.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

How is a stationary wave formed?

A

Superposing two progressive waves travelling in opposite directions with the same λ, f and v.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What 4 things do you need for a stationary wave to occur?

A

The same speed.
The same wavelength.
The same frequency.
Travelling in opposite directions.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What are nodes?

A

Points within a stationary wave that don’t move. Usually have zero amplitude.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What are antinodes?

A

Points within a stationary wave that rapidly oscillate between maximum positive and maximum negative amplitude.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the difference (in wavelength) between two nodes or two antinodes?

A

1/2 λ

35
Q

How do you calculate the phase difference using nodes?

A

ϕ= n x π

Where n is the number of nodes simplified to 1 or 2 between two points.

36
Q

What sort of boundary condition will result in antinodes at each end?

A

A tube with open ends.

37
Q

What sort of boundary condition will result in an antinode at one end and a node at the other?

A

A tube with one end closed and the other open.

38
Q

What are some example wavelengths for a tube with both ends open?

A

1/2λ, λ, 3/2λ etc.

39
Q

What are some example wavelengths for a tube with one end open and the other closed (Boundary conditions)?

A

1/4λ, 3/4λ, 5/4λ

40
Q

How do you form a stationary wave using a string?

A

By fixing it at both ends and sending vibrations through it.

41
Q

What does the first harmonic look like?

A

When the wave has a node at either end and an antinode in the centre.

42
Q

What properties of a wave can change when it travels from a thick string to a thin string?

A

The propagation speed.
Amplitude.
Wavelength.

43
Q

What points in a stationary wave vibrate in phase?

A

All the points between a pair of nodes.

44
Q

If two sound waves of the same frequency move away from each other what will it sound like?

A

A sound with loudness that will rise and fall periodically.

45
Q

How can you change the note created by a string without changing the length of the string?

A

By changing the mass per unit length of the string.
By changing the tension on the string.

46
Q

What 3 factors affect the main frequency of a string?

A

μ = Mass per unit length (kgm⁻¹)
l = length of string (m)
T = Tension in the string (N)

47
Q

What equation is used to calculate wave speed along a string?

A

v = √T/μ

v = speed, T = tension, μ = mass per unit length

48
Q

What is double slit interference?

A

When light passes through two slits it diffracts producing two coherent sets of waves. Interference is created between the two sets of diffracted waves.

49
Q

What is the name for the pattern created by double slit interference?

A

Young’s fringes

50
Q

In double slit interference what must the waves have to have an observable interference pattern.

A

The waves must be coherent. Meaning they have the same frequency and a constant phase difference.

51
Q

What will happen if double slit interference occurs with incoherent waves?

A

The interference pattern will continually change. Usually too quick for observation.

52
Q

What is a bright fringe?

A

When the light from one slit is reinforced by the light from the other slit. This means at a bright fringe both waves will be in phase and will constructively interfere (peak to peak/trough to trough).

53
Q

What is a dark fringe?

A

When the light from the two slits cancel each other due to being in anti phase with each other.

54
Q

What is different in the pattern created by single slit and double slit interference?

A

Single slit:
2x width for central fringe.
As you move away from the centre the bright fringes greatly decrease in intensity.

Double slit:
Fringes have same width.
All fringes of same (similar) intensity.

55
Q

How do you calculate the separation between gratings on a diffraction plate?

A

d = 1/N

where N = the number of line per unit distance.

56
Q

What formula can be used to calculate wavelength (Diffraction Grating)?

A

dsinθ = nλ

dsinθ/n = λ

57
Q

How does grating spacing affect the angle of diffraction?

A

As grating spacing increases diffraction decreases.

58
Q

Describe Huygen’s principle.

A

As light waves are diffracted each end of a slit acts like a source of waves. These waves interfere to create a interference pattern. When the waves interfere constructively they form a bright fringe. When they interfere destructively they cancel out and form a dark fringe.

59
Q

Describe the interference pattern created by diffracted white light across a double slit.

A

Central bright fringe of white light where all the wavelengths of light have interfered.
Spectrum of bright fringes as you move from the centre where different wavelengths within the light have interfered constructively creating an inner lining of blue and an outer lining of red.
Intensity of fringes will very slightly decrease.
The width of a spectrum of these fringes will be the same as the central fringe.

60
Q

What does coherent mean (waves)?

A

Same frequency.
Same phase difference.

61
Q

Define monochromatic light.

A

Light of only one wavelength.

62
Q

How will increasing mass per unit length of a string (μ) affect the note it produces?

A

Higher mass per unit length means sound wave travels at lower speed ∴ means lower frequency and a lower note.

63
Q

How will tension (T) affect the note a string produces?

A

The higher the tension the faster the wave will travel and the higher the note produced will be.

64
Q

When referring to wave/string equations what do “n” and “L” stand for?

A

n = number of loops along a string, the nth harmonic
L = Length of a loop

65
Q

How do you calculate the main frequency of a string?

A

fn = (n/2L) x (√T/μ)
f = (1/2L) x (√T/μ)

66
Q

Why is cladding used in fibre optics?

A

To prevent the crossover of data between fibres.
Prevents signal degradation from light escaping the core.
Prevents physical damage to the fibre.

67
Q

What is the equation to find fringe separation distance?

A

W = λD/s

W = fringe separation distance, S = distance between slits, D = Distance from slits to screen

68
Q

Why is a stationary wave formed when a guitar string is plucked?

A

Two progressive waves move from centre two each end and reflect back. This means they are travelling in opposite directions and have the same λ, f and v. The waves then interfere creating a stationary wave.

69
Q

How does the use of a single slit make the waves sufficiently coherent?

A

Single slit acts as a single point of light diffracting to both slits. (Same frequency)
The paths lengths between the single and double slits are fixed. (Sameϕ)

70
Q

How could apparatus be arranged for more accuracy (double slit Q)?

A

Increase the distance which decrease percentage uncertainty.
Measure across multiple maxima which decreases percentage uncertainty.

71
Q

What is a spectrometer used for?

A

Spectral analysis of light from stars
Analysing the composition of a star
Chemical analysis

72
Q

When light is passed through a spectrometer what is the difference between light emerging at first order and light at second order?

A

The light at 1st order will appear white.
The light at 2nd order will be a spectrum.

73
Q

Give a piece of evidence that suggests light also posseses wave properties.

A

Double slit interfernece creates interference patterns when light constructively and destructively interferes.
Only waves can interfere.

74
Q

What occurs in the photoelectric effect?

A

When light (photons) of a high enough frequency (energy) are incident on a metal electrons near the surface of the metal will be emitted.

75
Q

What is the equation for strain energy of a string?

A

E = ½Fd

d = extension of string

76
Q

Explain how sound from two loudspeakers increases and decreases in volume as you walk parallel to them?

A

Sound waves from either speaker superpose at a point.
When the two waves are in phase they produce a maximum.
Walking away produces a path difference which makes the destructively interfere causing a reduction in amplitude.

77
Q

Equation for angle of refraction of light between mediums?

A

n1sinθ = n2sinθ

78
Q

How to calculate critical angle?

A

sinθ = n2/n1

79
Q

What happens to a signal if two transmitters are moved further and further out of sync?

A

The signal goes through multiple maxima and minima.
Reflected and direct waves interfere.
Path difference increases as plate is moved.
Phase difference changes so signal strength changes.

80
Q

When might Young’s slit equation not be suitable?

A

If the slits are not narrow.
If the slit separation is NOT greatly shorter than the screen distance.

81
Q

When is Young’s double slit equation not suitable?

A

Screen distance must be a lot greater than slit separation.

82
Q

How can you find if a wavelength is suitable for a Young’s double slit experiment?

A

Find the path difference of slits.
Wavelength suitable if: path difference > λ/2

83
Q

How is a maximum produced (light diffraction)?

A

Light passes through slits and diffracts.
Path difference between slit sources is equal to nλ.
Waves are in phase at screen.
They superpose, creating a maximum.

A-level Physics (14 decks)

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