Waves Flashcards
Amplitude
A wave’s maximum displacement from its equilibrium position
Antinode
A position of maximum displacement in a stationary wave
Cladding
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
Coherence
Waves are coherent if they have the same wavelength and frequency, as well as there being a fixed phase difference between them.
Diffraction Grating
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.
Diffraction
The spreading of waves as they say pass through a gap of similar magnitude to their wavelength
Electromagnetic waves
Waves that consist of perpendicular electric and magnetic oscillations
Frequency
The number of waves that pass a point in a unit time period. It is the inverse of time period
Interference
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.
Laser
A light source that produces a collimated and coherent beam.
Longitudinal wave
A wave with oscillations that are parallel to the direction of energy propagation. Sound like waves are longitudinal
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.
Node
A position of minimum displacement in a wave
Optical fibre
A thin glass through which signals are passed through. Optical fibres usually have cladding surrounding them
Path difference
A measure of how far ahead a wave is compared to another wave, usually expressed in terms of wavelength
Phase difference
The difference in phase between two points on a wave. It is usually expressed in radians
Phase
A measure of how far through the wave’s cycle a given point on the wave is.
Polarisation
The restriction pf a wave so that it can only oscillate in a single plane. This can only occur for transverse waves.
Pulse broadening
The elongation of a signal passed down an optical fibre, commonly due to modal or material dispersion.
Refractive index
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.
Snell’s law
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
Speed
The product of a wave’s 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 inside boundary of the fibre, meaning no radiation passes out.
