3. Waves- Definitions

Question 1

Aplitude

Answer 1

A wave’s maximum displacement from its equilibrium position

Question 2

Antinode

Answer 2

A position of maximum displacement of a stationary wave

Question 3

Cladding

Answer 3

A protective layer on fibres that increase tensile strength, prevent scratches and to prevent signal transfer between adjacent fibres

Question 4

Coherence

Answer 4

Waves are coherent if they ave the same wavelength , frequency and have a fixed phase difference between them

Question 5

Diffraction grating

Answer 5

A grating with hundreds of slits per milimetre that result in sharper interference patterns . They are used to calculate atomic spacing and analyse elements

Question 6

Diffraction

Answer 6

The spreading of waves as they pass through a gap similar to their wavelength

Question 7

Electromagnetic waves

Answer 7

Waves that consist of perpendicular electric and magnetic oscillations

Question 8

Frequency

Answer 8

The number of times a wave passes through a point in a unit time period

Question 9

Fringe spacing

Answer 9

The distance between 2 adjacent bright or dark fringes

Question 10

Interference

Answer 10

the name given to the superposition of waves that occurs when two waves meet. If the waves are in phase they constructively interfere , but if they are out of phase they will destructively interfere

Question 11

Longitudinal wave

Answer 11

A wave with oscillations parallel to the direction of energy transfer ei: sound waves

Question 12

Material dispersion

Answer 12

Waves of different wavelengths travel at slightly different speeds through an optical fibre and so reach the end of the fibre at slightly different times, causing pulse broadening. The use of monochromatic light fixes this

Question 13

Modal dispersion

Answer 13

Waves enter an optical fibre at slightly different angles,
meaning the distance each beam has to travel is slightly different. This leads to the beams reaching the end at different times and so causes pulse broadening

Question 14

Node

Answer 14

A position of minimum displacement in a stationary wave

Question 15

Optical fibre

Answer 15

A thin glass fibre through which signals are transmitted

Question 16

Path difference

Answer 16

A measure of how far ahead a wave is from another wave

Question 17

Phase difference

Answer 17

The difference in phase between 2 points in a wave

Question 18

Phase

Answer 18

A measure of how far through a cycle a given point on the wave

Question 19

Polarisation

Answer 19

The restriction of a wave so it can only oscillate in 1 plane . This can only occur for transverse waves

Question 20

Pulse broadening

Answer 20

The elongation of a signal passed down an optical fibre

Question 21

Refractive index

Answer 21

A material property that is given by the ratio between the speed of light in a vacuum to the speed of light in the material

Question 22

Snell’s law

Answer 22

A law linking a waves angle of incidents to the waves angle of refraction, with the use of the refractive index’s of the mediums involved

Question 23

Speed

Answer 23

The product of a waves frequency and wavelength

Question 24

Stationary wave

Answer 24

A wave that stores but does not transfer energy

Question 25

Total internal reflection

Answer 25

An effect that occurs in optical fibres, where full reflection occurs at the edge of the boundary

Question 26

Transverse wave

Answer 26

A wave with oscillations perpendicular to the direction of energy propagation. Electromagnetic waves are an example of these

Question 27

Wavelength

Answer 27

The distance between 2 identical positions on 2 adjacent waves

Question 28

Young’s double slit experiment

Answer 28

An experiment that demonstrates the diffraction of light by passing monochromatic light through 2 narrow strips and observing the pattern of light and dark fringes