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Physics > Waves Chapter 5 > Flashcards

Waves Chapter 5 Flashcards

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1
Q

What are longitudinal waves

A

Waves which the direction of vibrating of the particles is parallel to along the direction in which the wave travels
Waves that are like a slinky

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2
Q

What are transverse waves

A

Waves in which the direction of vibration is perpendicular to the direction in which wave travels
Goes up and down

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3
Q

What is polarisation

A

Where it involves transverse waves which are in a plane polarised if the vibrations stay in one plane only.

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4
Q

Polarisation from one plane to another

A

Polarised from one plane to another the waves are in polarised

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5
Q

What happens if unpolarised light passes through a Polaroid

A

It transmits light is polarised as the filter only allows through light which vibrates in a certain direction, according to the alignment of its molecules

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6
Q

What happens if Unpolarised light passes through two Polaroid filters

A

The transmitted light intensity changed if one Polaroid is turned relative to the other one.

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7
Q

What happens if Unpolarised light passes through two Polaroid filters
Pt2

A

Crossed and transmitted intensity is a minimum this position shows the polarised light from the first filter cannot pass through the second filter as the alignment of molecules in the second filter is at 90⁰ to the alignment in the first filter.

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8
Q

Phase difference

A

Phase of a vibrating particles at a certain time is the fraction of a cycle it has completed since the start of the cycle.
The phase difference is between two particles vibrating at the same frequency is the fraction of a cycle between the vibrations of the two particles measured either degrees or radians.

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9
Q

Wave speed info

A

Higher the speed and frequency of the wave shorter the wavelength.

Higher the frequency close together the wave peaks are

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10
Q

Wave speed equation

A

Wave speed = c = f x λ

C = distance travelled in one cycle / time taken for one cycle

C = λ÷ 1÷f
= fx λ

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11
Q

Parts of a wave

A

Amplitude - from middle line to the height of ether wave

Wavelength - from one wavelength to another

Trough - from the bottom of the wave to the middle line

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12
Q

Key terms

Displacement

A

Of a vibrating particle is it’s distance and direction from its equilibrium position

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13
Q

Key terms

Amplitude

A

Maximum displacement of a vibrating particle for a transverse wave it is distance from the middle to the peak of the wave.

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14
Q

Key terms

Wavelength

A

Least distance between two adjacent vibrating particles with the same displacement and velocity at the same time

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15
Q

Key terms

Cycle

A

When a vibrating particle is displaced unit is return to its stored.

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16
Q

Key terms

Period

A

Period of a wave is the same time for one complete wave to pass a fixed point

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17
Q

Key terms

Frequency

A

Numb of cycles of wave that pass a point per second

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18
Q

What’s a progressive wave

A

To distinguish them from stationary waves. They combine at fixed points along the rope to form point of no displacement or nodes along the rope. At each node the two sets of waves are always 180⁰ out of phase so they cancel each other out.

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19
Q

Antinode

A

Fixed point in a stationary wave pattern where amplitude is maximum

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20
Q

Node

A

fixed point in a stationary wave pattern where the amplitude is zero

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21
Q

Stationary wave

A

Stationary wave is formed when two progressive waves pass through each other
This can be achieved on a string tension by fixing both ends and making the middle part vibrate so progressive wave and travel towards each end reflects at the end and then pass through each other

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22
Q

Superposition

A

When two waves meet they pass through each other at a certain point where they meet, they combine for an instant before they move apart
The total displace at a point is equal to the sum of the individual displacement at that point

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23
Q

What happens when two crest meet

A

Make a super test created by two waves reinforce each other

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24
Q

What happens when two trough meet

A

Make a supertrough

25
Q

What happens when a crest and a trough meet

A

If the both have the same amplitude the resultant displacement is zero the waves Cancel each other out if they are not the same amplitude the resultant is called a minimum

26
Q

Frequency

A

F= c/λ

27
Q

Wave speed

A

fλ = c

28
Q

Wavelength

A

λ=c/f

29
Q

The refractive index

A

N= sin i / sin r

30
Q

Wavefront

A

Lien that connects all the point on a wave that are in phase

31
Q

Refraction

A

Change of direction due to a change of speed caused by a change in density

32
Q

What occurs to refraction

A

Retraction occurs because the speed of the light waves is ditterent in each substance. The amount of refraction that takes place depends on the speed of the waves in each substance.

33
Q

Snells law calculation 1

A 
Cst = sin(r) x XY
Ct= sin(i) x XY
Cst/sin(r) = XY = ct/sin(i)

Rearrange
Ct/cst = sin(i)/sin(r)

C/cs = sin(i) / sin(r) = N

34
Q

Snells law calculation 2

A

N1 x sin(i) = N2 x sin(r)

35
Q

Refractor equation

A

N1 x sin(i) ÷ N2 = Angle of refraction

36
Q

Incidence equation

A

Sin(r) x N2 / N1

37
Q

Critical angle

A

Sin0₁ = N2 / N1

38
Q

What is critical angle

A

The angle of incidence where the refracted ray travels along the boundary between the two medium

Angle of i = critical
i = c

39
Q

Total internal reflection occurs when

A
  1. i > c angle of incidence is larger than the critical angle
  2. Light travels from more dense to less dense medium

Sin0c = N2/N1

40
Q

Optical fibres

A

Optical fibres are used in medical endoscopes to see inside the
body, and in communications to carry light signals.

41
Q

What does optical fibres do

A

They allow pulses of light that enter at one end from a transmitter to reach a receiver at the other end

42
Q

Total internal reflection takes place when

A

The cor cladding boundary at any point where two fibres are in direct contact light would cross from one fibre to the other if there were no cladding.

43
Q

Medical endoscope

A

medical endoscope contains two bundles of fibres. The endoscope
is inserted into a body cavity, which is then illuminated using light sent
through one of the fibre bundles. A lens over the end of the other fibre
bundle is used to form an image of the body cavity on the end of the
fibre bundle. The light that forms this image travels along the fibres to
the other end of the fibre bundle where the image can be observed. This fibre bundle needs to be a coherent bundle, which means that the Fibre ends at each end are in the same relative positions.

44
Q

Interference

A

Occurs when two coherent progress waves travelling in the same direction
Similar amplitude
Same frequency constant phase difference
Two waves diffract and super pose to form a regular interference pattern

45
Q

Constructive interference

A

Occurs when the position of the path is difference a whole number of wavelength nλ

46
Q

Destructive interference

A

Occurs when the path difference = a whole number plus half a wavelength n + 1/2 λ

47
Q

Fringe separation

A

W= λ x D / s

D = distance 
λ = wavelength 
S = split spacing
W = fringe separation
48
Q

Double slit equation

A

S1 x P - S2 x P = m x λ

Two slits S1,S2
P point on the screen
M =1,2,3,4 etc …

49
Q

Wavelength and colour
650nm
350nm

A
  1. Red light

2. Violet

50
Q

Single slit diffraction width

A

W = λ / a x 2D

A = single slit
D= split screen distance
51
Q

Through a single slit

A

The central fringe is twice as wide as each of the outer fringes
Each of the outer fringes is the same width

52
Q

Intensity

A

Peak intensity of each fringe decreases with distance from the centre
The outer fringes are much less intense than the central fringe

53
Q

Diffraction wavelength

A

Greater the wavelength the wider the fringe

Width of the central fringe is proportional to the wavelength

54
Q

Diffraction grating

A

diffraction grating consists of a plate with many closely spaced
parallel slits ruled on it. When a parallel beam of monochromatic light is directed normally at a diffraction grating, light is transmitted by the grating in certain directions only.
This is because:
the light passing through each slit is diffracted

55
Q

Diffraction grating equation

A

D x sin0 = n x λ

56
Q

Stationary wave equation

A

F= 1/ 2x L √ t/u

F= frequency 
L = length 
T= tension 
U = mass per unit length
57
Q

Describe when some light is refracted and some light is reflected at a boundary

A

Internal reflection

58
Q

Modal dispersion

A

The lengthening of a light pulse as it travels along an optical fibre due to rays that repeatedly undergo total internal reflection having to travel along distance than rays that undergo fewer total internal reflections

Physics (19 decks)

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