3. Waves- Definitions Flashcards
Aplitude
A wave’s maximum displacement from its equilibrium position
Antinode
A position of maximum displacement of a stationary wave
Cladding
A protective layer on fibres that increase tensile strength, prevent scratches and to prevent signal transfer between adjacent fibres
Coherence
Waves are coherent if they ave the same wavelength , frequency and have a fixed phase difference between them
Diffraction grating
A grating with hundreds of slits per milimetre that result in sharper interference patterns . They are used to calculate atomic spacing and analyse elements
Diffraction
The spreading of waves as they pass through a gap similar to their wavelength
Electromagnetic waves
Waves that consist of perpendicular electric and magnetic oscillations
Frequency
The number of times a wave passes through a point in a unit time period
Fringe spacing
The distance between 2 adjacent bright or dark fringes
Interference
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
Longitudinal wave
A wave with oscillations parallel to the direction of energy transfer ei: sound waves
Material dispersion
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
Modal dispersion
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
Node
A position of minimum displacement in a stationary wave
Optical fibre
A thin glass fibre through which signals are transmitted
Path difference
A measure of how far ahead a wave is from another wave
Phase difference
The difference in phase between 2 points in a wave
Phase
A measure of how far through a cycle a given point on the wave
Polarisation
The restriction of a wave so it can only oscillate in 1 plane . This can only occur for transverse waves
Pulse broadening
The elongation of a signal passed down an optical fibre
Refractive index
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
Snell’s law
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
Speed
The product of a waves frequency and wavelength
Stationary wave
A wave that stores but does not transfer energy
Total internal reflection
An effect that occurs in optical fibres, where full reflection occurs at the edge of the boundary
Transverse wave
A wave with oscillations perpendicular to the direction of energy propagation. Electromagnetic waves are an example of these
Wavelength
The distance between 2 identical positions on 2 adjacent waves
Young’s double slit experiment
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
