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Flashcards in waves Deck (33)
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1

define a progressive wave

an oscillation of particles/fields in a medium that transfers energy from one point to another, without transferring material

2

give an equation for wave speed

c=fλ

3

give an equation for frequency, with relation to period.

f= 1/T

4

define a transverse wave

the direction of oscillation is perpendicular to the direction of motion of the energy. i.e. electromagnetic

5

what is a longitudinal wave

the direction of the oscillation is parallel to the direction of motion of the energy i.e. sound waves

6

define polarization, and give an application

only allowing a wave to oscillate on one plane,
van be used in sunglasses/aerials

7

state the equation for the law of reflection

θ1=θ2

8

state the equation for refractive index

n =c/c(s)
where c is the speed of light and c(s) is the speed of light in the material

9

give snell's law of refraction

n(a)sinθ(a) = n(b)sinθ(b)

10

what properties are affected by refraction

wavelength varies, wave speed varies

11

what is the refractive index of air

1

12

what is total internal reflection

where no refraction occurs if the angle of incidence is greater than the critical angle
sinθ =n(b)/n(a)

13

describe step index optical fibres, and the use of their cladding

- thin glass fibres that fire signals made of light pulses
- light undergoes TIR, so no light escapes
- cladding has a lower refractive index to ensure TIR happens
- cladding acts as protection for thin fibre

14

what is modal dispersion?

when light rays enter a fibre at different angles causing them to take longer to reach the end.

15

what is material dispersion, and how do you prevent it?

when different wavelengths travel at different speeds resulting in them arriving at different times
(can be overcome by using monochromatic light)

16

what is diffraction

waves spreading out after passing through a gap with a similar size to the wavelength

17

Define monochromatic

Single wavelength

18

Define coherent

Constant phase difference

19

State a safety precaution when using a laser

dont look into the laser

20

State and explain the effect of using a laser with a shorter wavelength on the maxima spacing in Young's double slit

Maxima closer together
use w=𝜆D/s

21

Use wave theory to explain how the fringe pattern is formed

Slits act as coherent sources
Waves diffract at slits
Waves superpose
Bright patches: constructive
Dark patches: destructive

22

State two requirements for two light sources to be coherent

Same wavelength
Same phase

23

Explain how Young's double slit arrangement produces interference fringes, refer to width of first slit and coherence of second slits

Narrow single slit gives wide diffraction to ensure that both second slits are illuminated
Paths to second slits are of constant length giving constant phase difference
Light diffracted at slits and overlap and interfere
Where path lengths differ by whole number of wavelengths, constructive interference occurs producing a bright fringe

24

If Young's double slit was carried out with red light and then with white light, how would the two differ?

Central fringe would be white
Dark fringes would be closer together
Side fringes are spectra

25

State two ways a diffraction pattern on single slit would change if the slit became narrower

Increased separation
Lower intensity

26

State and explain what happens to angle θ in λ = d sin θ when wavelength decreases?

Angle θ gets smaller
As path difference gets smaller

27

Why will total internal reflection occur when light ray travels from water into glass?

TIR only occurs when ray travels from higher n to lower n

28

State and explain an advantage of a smaller diameter core in a fibre optic

Reduce multipath
Which would cause poor resolution

29

Define amplitude of a wave

The maximum displacement of the wave from the equilibrium position

30

What is an S-wave?

A secondary wave that is transverse