Waves Flashcards

1
Q

speed of light

A

c = 3 x 10^8 m/s

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2
Q

speed of sound

A

343 m/s

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3
Q

wavelength frequency speed

A

v = fλ

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4
Q

frequency, time period

A

T = 1/f

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5
Q

Polarization

A

waves of the transverse waves are limited to one plane of movement, while the rest is absorbed

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6
Q

polarising filters what they do

A

only waves oscillating in same direction as filter will pass through
2 filters perpendicular to each other won’t let through any light

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7
Q

uses of polarisation

A
  • polarised sunglasses to reduce glare
  • receiving areal and radio signals
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8
Q

stationary waves nodes and antinodes

A

node - no displacement
anti-node - point of max displacement

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9
Q

distance between two nodes

A

1/2 λ

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10
Q

Explain how standing wave is formed (3)

A
  • superposition
  • two waves of same frequency and amplitude
  • travelling in opposite directions
  • one is reflected
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11
Q

points between two nodes

A

points between two nodes all in phase

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12
Q

For first harmonic:
frequency, length, tension, μ

A

For first harmonic:
f = 1/2L sqrt(T/μ)

where μ is mass/length of string

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13
Q

standing wave with microwave practical setup

A

transmitter
metallic reflective plate 1/2λ away
movable detector in middle

when detector is at plate, min
when at middle, max

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14
Q

standing wave in a tube

A

at closed end: pressure antinode, displacement node

at open end: pressure node, displacement antinode

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15
Q

laser

A

monochromatic light (one wavelength) so light is coherent

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16
Q

double slit setup and result

A

laser which has similar wavelength to gap

result is equally spaces fringes

17
Q

single slit diffraction monochromatic

A

large central maxima with smaller less intense fringes on either side

18
Q

single slit diffraction white light

A
  • central maxima bright white
  • less wide less intense fringes on either side
  • fringes on either side would be spectrum which get more and more spread out
  • violet closest to maxima, red furthest
19
Q

diffraction

A

the spreading out of waves as they pass through a gap or around an obstruction

20
Q

single slit equation (destructive min)

A

dsin(θ) = mλ

where d is the slit width
m is the order of the min

21
Q

double slit equation

A

W = λD/s

where w is fringe spacing
D is from slits to screen
s is slit spacing

22
Q

diffraction grating equation and derivation

A

dsin(θ) = nλ

where d is the slit width
n is the order of the bright spot

derive on paper

23
Q

snells law

A

n1sin(θ1) = n2sin( θ2)

24
Q

refractive index, speed of light

A

n = c in air/ c in material

25
critical angle
angle of incidence when angle of refraction = 90 above which total internal refraction happens
26
show c, n1, n2 equation
n1 sin θ1 = n2 sin θ2 n1 sin θc = n2 sin θc = n2/n1
27
uses of total internal reflection
optic fibres
28
step index optic fibre
the refractive index of each component increases moving from the outside to the centre of the fibre
29
role of cladding in optic fibre
- Protect the thin core from damage and scratching - Prevent signal degradation through light escaping the core, which can cause information from the signal to be lost - It keeps the core separate from other fibres preventing information crossover
30
prisms
prisms will always totally internally reflect
31
approx λ for em waves
Radio waves - 1km Microwaves - 10 cm Infrared - 10^-5 Visible - 10^-6 Ultraviolet - 10^-8 X rays - 10^-10 Gamma - 10^-12
32
coherent (waves)
have same wavelength, frequency and are in phase
33
stationary wave experiment
- signal generator connected to vibration transducer - string going across a pulley at end of bench with a mass hung on one end - measure mass and length of string to find μ - find tension - vary frequency of signal generator until first harmonic equation
34
2 reasons for signal degradation and effects on signal
- absorption by material causes loss in amplitude - dispersion causes broadening
35
Two types of dispersion (signal degredation)
- modal - light enters at different angles - material - not all light had same wavelengths
36
diffraction grating limitations (from equation)
d sin(θ) = nλ sin(θ) can't be greater than 1 so only certain values of n order possible
37