waves

Question 1

define amplitude

Answer 1

a wave’s max displacement from its equilibrium position

Question 2

define antinode

Answer 2

a position of max displacement in a stationary wave

Question 3

define cladding

Answer 3

a protective layer on an optical fibre to improve the tensile strength of the fibre

Question 4

what does cladding do?

Answer 4

prevents scratching and signal transfer between adjacent fibres

Question 5

when are waves coherent?

Answer 5

when they have the same wavelength and frequency with a fixed phase difference between them

Question 5

define diffraction grating

Answer 5

a grating with hundreds of slits per mm, resulting in sharper interference patterns

Question 5

what are diffraction gratings used for?

Answer 5

calculating atomic spacing and to analyse elements

Question 6

define diffraction

Answer 6

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

Question 7

define electromagnetic waves

Answer 7

waves that consist of perpenpendicular electric and magnetic oscillations

Question 8

define frequency

Answer 8

the number of waves that pass a point in a time period

Question 9

define fringe spacing

Answer 9

the distance between two adjacent bright or two adjacent dark fringes.

Question 10

define interference

Answer 10

the superposition of waves that occurs when two waves meet

Question 11

what interference occurs when waves are in phase?

Answer 11

constructive interference

Question 12

what interference occurs when waves are out of phase?

Answer 12

destructive interference

Question 13

define laser

Answer 13

a light source that produces a coherent monochromatic beam

Question 14

define longitudinal wave

Answer 14

a wave with oscillations parallel to the direction of energy

Question 15

give an example of a longitudinal wave

Answer 15

sound waves

Question 16

define material dispersion

Answer 16

waves of different wavelengths travel at slightly different speeds through an optical fibre so they reach the end at different times

Question 17

what does material dispersion cause?

Answer 17

pulse broadening

Question 18

how would you fix material dispersion?

Answer 18

by using monochromatic light

Question 19

define modal dispersion

Answer 19

waves enter an optical fibre at slightly different angles, meaning the distance each beam has to travel is slightly different

Question 20

what does modal dispersion cause?

Answer 20

pulse broadening

Question 21

define node

Answer 21

a position of min displacement in a stationary wave

Question 22

define optical fibre

Answer 22

a thin glass fibre through which signals are passed through

Question 23

define path difference

Answer 23

a measure of how far ahead a wave is compared to another wave.

Question 24

define phase difference

Answer 24

the difference in phase between two points on a wave

Question 25

define phase

Answer 25

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

Question 26

define polarisation

Answer 26

the restriction of a wave so that it can oscilate in a single plane

Question 27

what type of wave can polarisation occur for?

Answer 27

transverse waves

Question 28

define pulse broadening

Answer 28

the elongation of a signal passed down an optical fibre

Question 29

define refractive index, n

Answer 29

the ratio of the speed of light in a vacuum and in a given material

Question 30

what is snell’s law

Answer 30

law linking the wave’s angle of incidence to the angle of refraction using the refractive indexes of the mediums involved.

Question 31

define stationary wave

Answer 31

a wave that stores but doesn’t transfer energy

Question 32

define total internal reflection

Answer 32

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

Question 33

define transverse wave

Answer 33

a wave with oscillations that are perpendicular to the direction of energy propagation

Question 34

give an example of a transverse waves

Answer 34

electromagnetic waves

Question 35

how to measure wavelength?

Answer 35

from peak to peak, or trough to trough

Question 36

define wavelength

Answer 36

the distance between two identical positions on two adjacent waves.