Waves

Question 1

Progressive wave

Answer 1

A wave that transfers energy from one place to another without transferring any material

Question 2

Stationary wave

Answer 2

The superposition of two progressive wave of equal amplitude moving in opposite directions. They transfer NO energy unlike progressive waves

Question 3

Refraction

Answer 3

The change in direction of a wave as it enters different medium. Caused by a change in density causing a change in speed

Question 4

Diffraction

Answer 4

The spreading of waves as it passes through a gap. Occurs most when the gap is the same size as the wave

Question 5

Amplitude

Answer 5

Maximum displacement from the equilibrium postion

Question 6

Displacement

Answer 6

How far a point on a wave is from the equilibrium position

Question 7

Wavelength

Answer 7

The length of one whole wave or wave cycle. Minimum distance between two identical points on wave i.e peak to peak

Question 8

Period

Answer 8

Time taken for one complete wave cycle to occur

Question 9

Frequency

Answer 9

The number of complete wave cycles passing a given point per second

Question 10

Phase difference

Answer 10

Always measured in degrees or radians, the amount by which one wave lags behind another

Question 11

Path difference

Answer 11

The amount by which the path taken by one wave is longer than another, usually given as a number of wavelength

Question 12

Transverse Wave

Answer 12

Oscillation of medium is perpendicular to energy transfer, eg all EM waves

Question 13

Longitudinal wave

Answer 13

The oscillation of medium is parallel to energy transfer eg sound waves or mechanical waves

Question 14

Polarisation

Answer 14

The removal of all but one planes of oscillation from a wave, done by a polarising filter

Question 15

These types of wave cannot be polarised

Answer 15

Longitudinal

Question 16

Rarefaction

Answer 16

The uncompressed part of a longitudinal wave

Question 17

Normal

Answer 17

a line perpendicular to a surface used to make angular measurements

Question 18

Refractive index

Answer 18

the ratio between speed of light in vacuum and speed of light in a particular material

Question 19

Refractive index of air

Answer 19

1

Question 20

Critical angle

Answer 20

During refraction it is the angle of incident light which results in the angle of refraction being 90 degrees

Question 21

Total Internal Reflection

Answer 21

Occurs at angles above the critical angle. All light is reflected back inside the material

Question 22

Purpose of cladding on optic fibres

Answer 22

Has a lower refractive index than the core so increases the critical angle (compared to air/no cladding) leading to less modal dispersion

Question 23

Model dispersion

Answer 23

The spreading of a signal in an optic fibre because rays entering at different angles travel different distances therefore take different times to travel the fibre.

Question 24

Material dispersion

Answer 24

The spreading of a signal due to different colours travelling at different speeds inside a material

Question 25

Monochromatic light

Answer 25

Light that consists of one frequency

Question 26

Coherent

Answer 26

Constant phase relationship

Question 27

Superposition

Answer 27

When two waves pass each other and combine forming a wave that is the vector addition of both displacements

Question 28

Constructive Interference

Answer 28

When two waves with no phase difference superpose they will produce a maxima

Question 29

Destructive Interference

Answer 29

When two wave superpose and they have a phase difference of 180 or Pi radians they will produce a minima

Question 30

Number of radians in a complete wave cycle

Answer 30

2 pi Radians