Waves

Question 1

Amplitude

Answer 1

A wave’s maximum displacement from its equilibrium position

Question 2

Antinode

Answer 2

A position of maximum displacement in a stationary wave

Question 3

Cladding

Answer 3

A protective layer on an optical fibre to improve the tensile strength of the fibre, prevent scratching and to prevent signal transfer between adjacent fibres

Question 4

Coherence

Answer 4

Waves are coherent if they have the same wavelength and frequency, as well as there being a fixed phase difference between them.

Question 5

Diffraction Grating

Answer 5

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

Question 6

Diffraction

Answer 6

The spreading of waves as they say pass through a gap of similar magnitude 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 waves that pass a point in a unit time period. It is the inverse of time period

Question 9

Interference

Answer 9

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

Question 10

Laser

Answer 10

A light source that produces a collimated and coherent beam.

Question 11

Longitudinal wave

Answer 11

A wave with oscillations that are parallel to the direction of energy propagation. Sound like waves are longitudinal

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

Node

Answer 13

A position of minimum displacement in a wave

Question 14

Optical fibre

Answer 14

A thin glass through which signals are passed through. Optical fibres usually have cladding surrounding them

Question 15

Path difference

Answer 15

A measure of how far ahead a wave is compared to another wave, usually expressed in terms of wavelength

Question 16

Phase difference

Answer 16

The difference in phase between two points on a wave. It is usually expressed in radians

Question 17

Phase

Answer 17

A measure of how far through the wave’s cycle a given point on the wave is.

Question 18

Polarisation

Answer 18

The restriction pf a wave so that it can only oscillate in a single plane. This can only occur for transverse waves.

Question 19

Pulse broadening

Answer 19

The elongation of a signal passed down an optical fibre, commonly due to modal or material dispersion.

Question 20

Refractive index

Answer 20

A material property that is equal to the ratio between the speed of light in a vacuum, and the speed of light in a given material.

Question 21

Snell’s law

Answer 21

A law linking a wave’s angle of incidence to its angle of refraction, with the use of the refractive indexes of the mediums involved

Question 22

Speed

Answer 22

The product of a wave’s frequency and wavelength

Question 23

Stationary wave

Answer 23

A wave that stores, but does not transfer, energy

Question 24

Total internal reflection

Answer 24

An effect that occurs in optical fibres, where full reflection occurs at the inside boundary of the fibre, meaning no radiation passes out.

Question 25

Transverse wave

Answer 25

A wave with oscillations that are perpendicular to the direction of energy propagation. Electromagnetic waves are transverse waves.

Question 26

Wavelength

Answer 26

The distance between two identical positions on two adjacent waves. Measured from peak to peak and trough to trough

Question 27

Young’s Double-slit Experiment

Answer 27

An experiment that demonstrates the diffraction of light by passing monochromatic light across two narrow slits and observing the resulting pattern of bright and dark fringes