Year 12 - Waves and Optics Flashcards
Amplitude
The maximum displacement of the oscillating particle from the equilibrium/rest position.
Anti-node
Points on a stationary wave that oscillate with maximum amplitude. This is due to Construction.
Cladding
The Core of a fibre optic is surrounded by a protective cladding
• keeps signals secure (1)
• reduces pulse broadening (1)
• it keeps most light rays in the core due to total internal reflection at boundary (1)
• it prevents scratching/damage of the core (1)
CoherentSource
Waves with the same wavelength/frequency and a constant phase relationship [constant phase difference].
Compression
A region where particles are close to one another (High pressure).
Construction
Two or more waves overlap in such a way that they combine to create a larger wave.
Critical Angle
Angle of incidence when the angle of refraction is equal to 90 degrees.
Destruction
Two or more waves overlap in such a way that they cancel each other out.
Diffraction
The bending or spreading out of waves, when they travel through a small opening or when they pass round a small obstacle.
Diffraction Grating
A grating with hundreds (Typically between 300 to 1000) of lines per millimetre, that cause diffraction when lights passes through.
EM Waves
Transverse waves composed of perpendicular oscillating electric and magnetic fields. Hence EM or Electromagnetic.
Frequency
The number of complete cycles per unit time.
Fringe Spacing
The distance between two adjacent bright fringes or two adjacent dark fringes.
Horizontal Polarisation
Transverse waves that only oscillate in the horizontal plane.
Intensity
The rate of transfer of energy (Power) per unit area.
Interference
The superposition of two or more coherent waves to produce regions of maxima and minima in space, according to the principle of superposition.
Laser
A light source that produces a coherent beam of light. The waves are identical, in phase, with a constant phase relationship.
Longitudinal Wave
Particle vibration same as (or parallel to) direction of propagation(or energy transfer).
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.
Maxima
Point of maximum constructive interference.
Minima
Point of maximum destructive interference.
Modal Dispersion
Waves enter an optical fibre at slightly different angles, meaning the distance each ray has to travel is slightly different. This leads to the rays reaching the end at different times and causes pulse broadening.
Monochromatic
Waves of a single wavelength/frequency.
Node
Points on a stationary wave of zero amplitude and appear to be fixed. This is due to Destruction.
Optical Fibre
A thin glass fibre through which light signals are passed through. The Core of Optical fibres usually has cladding surrounding it.
Path Difference
A measure of the difference in distances waves travel, due to taking different paths, usually expressed in terms of the wavelength.
Period
Period T is the time for one complete oscillation/cycle.
Phase
A measure of how far through the wave’s cycle a given point on the wave is. A whole cycle is 360 degrees or 2p radians.
Phase Difference
The difference in phase between two points on a wave. It is usually expressed in radians.The phase difference between two particles or two waves tells us how much a particle (or wave) is in front or behind another particle (or wave).
Polarisation
(only) transverse waves can be polarised, (oscillations) restricted to a single plane.
Polarised Light
Transverse waves that only oscillate in a single plane.
Progressive Wave
Transfers Energy without transferring matter.
Pulse Broadening
The elongation of a signal passed down an optical fibre, commonly due to modal or material dispersion.
Rarefaction
A region where the particles are furthest apart (Low pressure).
Refraction
The bending of light (it also happens with sound, water and other waves) as it passes from one transparent substance into another.
Refractive Index
The ratio of the speed of light in a vacuum and the speed of light in a substance
Relative Refractive Index
The Ratio of the speed of light in substance 1 compared to the speed of light in substance 2 at a boundary. Alternatively the Ratio of the refractive index of substance 2 compared to the refractive index of substance 1 at a boundary.
Stationary Wave
A wave which does not transfer energy from one place to another.
Stationary Wave Conditions
Superposition of 2 progressive waves, with the same frequency/wavelength and speed, travelling in opposite directions, with a phase difference of 180 degrees.
Superposition
When two waves of the same kind meet at a point in space, the resultant displacement at that point is the vector sum of the displacements that the two waves would separately produce at that point.
Total Internal Reflection
Reflection that occurs when light rays travel from a more optically dense medium to a less optically dense medium.
Transverse Wave
Particle vibration perpendicular to direction of propagation (or energy transfer).
Unpolarised Light
Transverse waves where the wave’s oscillations (or vibrations) exist in more than a single plane.
Vertical Polarisation
Transverse waves that only oscillate in the vertical plane.
Wave Displacement
Displacementis the distance moved by the particle from its equilibrium/rest position.
Wave Speed
The distance travelled by a wave per unit time.Measured in metres per second.
Wavelength
Thewavelengthis the distance between 2 adjacent points on a wave which are in phase with one another.
Young’s Double Slit Experiment
An experiment that demonstrates the diffraction of light by passing monochromatic light through two narrow slits and observing the resulting pattern of bright and dark fringes caused by the path differences.
Young’s Double Slit Experiment: Construction
Caused when the path difference of the 2 waves is an integer number of wavelengths. E.g. Path Diff=nl.
Young’s Double Slit Experiment: Destruction
Caused when the path difference of the 2 waves is an integer number of half wavelengths. E.g. Path Diff=(l/2+n).
