Waves

Question 1

What is the definition of a progressive wave

Answer 1

a wave that transfers energy from one point in space to another, without transferring matter

Question 2

what is a transverse wave

Answer 2

A wave where occupations at right angles to the direction of travel and energy

Question 3

What are examples of transverse waves

Answer 3

electromagnetic waves, secondary seismic waves (s-waves), the top layer of water

Question 4

what is longitudinal waves

Answer 4

where the oscillations are parallel to the direction of travel

Question 5

what are examples of longitudinal waves

Answer 5

sound waves , primary seismic waves (p-waves)

Question 6

what is amplitude

Answer 6

the maximum displacement of a wave

Question 7

what is frequency

Answer 7

the number of waves each second

Question 8

what is the time period of a wave

Answer 8

the time for a complete wave to pass

Question 9

what is phase difference

Answer 9

how far apart two waves are. can be expressed in terms of numbers of wavelengths, degrees, or radians.

Question 10

what is the wave equation

Answer 10

velocity = frequency * wavelength

Question 11

what is polarisation, and what kind of wave does it work for

Answer 11

restricting the oscillation of a wave to one plane only. Only works for transverse, not longitudinal.

Question 12

what is superpositions

Answer 12

2 waves meeting in phase

Question 13

what is diffraction

Answer 13

when waves pass through a gap, they spread out. if the wavelength = gap size, the diffraction is maximum

Question 14

what does coherent mean

Answer 14

waves with the same frequency, same wavelength, and a constant phase difference

Question 15

To achieve a stationary interference pattern, what must two wave sources be

Answer 15

coherent

Question 16

what is path difference

Answer 16

the difference in length between two waves which meet at a point. measured in metres or fractions of wavelength

Question 17

what is monochromatic light

Answer 17

light with a single frequency and wavelength

Question 18

what do the words incident normally mean?

Answer 18

light hitting a surface at 90 degrees (perpendicular)

Question 19

what is a diffraction grating

Answer 19

a series of parallel lines on a piece of glass. the spaces between lines act as slits

Question 20

what is diffraction grating rating

Answer 20

the number of lines per mm

Question 21

how to find slit separation from grating rating

Answer 21

d = 1/grating rating

Question 22

what is the diffraction grating formula

Answer 22

d * sinθ = n * λ

Question 23

what is wave intensity

Answer 23

progressive waves transfer energy, and the energy passing each second through an area of 1m³ is the intensity.

Question 24

what is the formula for intensity

Answer 24

I = P / A

Question 25

what is a stationary/standing wave

Answer 25

the superposition of two progressive waves travelling in opposite directions with equal frequency and similar amplitude

Question 26

how to find the refractive index of material x

Answer 26

nₓ = c / cₓ

Question 27

what is the approx. refractive index of air

Answer 27

1

Question 28

what is snells law

Answer 28

n₁ * sinθ₁ = n₂ * sinθ₂ when θ₁ < θ₂ or n₁ < n₂ θ₁ = angle of incidence θ₂ = angle of refraction

Question 29

what is the formula for critical angle

Answer 29

sin theta = n2 / n1

Question 30

what happens when angle of incidence is >, =, < critical angle

Answer 30

incidence < critical: most light refracted, some reflected incidence = critical: most refracted along boundary, some reflected incidence > critical: total internal reflection occurs

Question 31

why do optical fibres need cladding

Answer 31

cladding protects against scratching, avoids crosstalk, avoids signal broadening

Question 32

what is multimodal dispersion, and how to prevent it

Answer 32

if material with small critical angle used for optical fibre, rays will take a different amount of time to reach the end. to prevent use cladding, fibre with a small diameter, or repeaters so pulse is reformed.

Question 33

what is the transmission rate

Answer 33

the number of pulses per second. it is greater when there is less modal dispersion. occurs with smaller diameter optical fibres.

Question 34

what are uses of optical fibres

Answer 34

fibre broadband, telephone signals, decoration