AS Waves
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- Created by: ravioli
- Created on: 14-12-16 21:24
What does a wave do?
They transport energy from one place to another (this is also known as a progressive wave)
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Define amplitude
Point of maximum displacement on a wave from the equilibrium position
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Define frequency
1/T (number of oscialltions per minute)
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Define wavelength
the shortest distance between two particles that are oscillating in phase.
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Define a period
The time taken for one complete oscillation of a particle in the wave.
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What are mechanical waves?
Mechanical waves use particles to transfer energy (neighbouring particles bump into each other and set their neighbours moving). Eg. sound waves
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What are electromagnetic waves?
Electromagnetic waves don't use particle vibration to transfer their energy and can therefore travel through a vacuum. e.g. light
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Longitudinal wave
Vibrations are parallel to the direction of propagation e.g. sound
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Tranverse wave
Vibrations are perpendicular to the direction of propagation e.g light
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What is the direction of displacement of particles/ fields relative to?
They are relative to the direction of energy propagation
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Define 'phase'
A measurement of the position of a certain point along the wave cycle
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Define 'phase difference'
The amount by which one wave lags behind another wave
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Do all EM waves travel at the same speed in a vacuum?
Yes, all EM waves travel at a speed of 3.00 * 10^8 m/s in a vacuum
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What is polarisation evidence of?
Polarisation is evidence for the nature of transverse waves
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Polarisation in the real world
1. Glare reduction - where unpolarised light hits a glass block, and the unpolarised light reflects back off and the reflected light is paritally polarised - some of the light travels in one direction)
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How does the superposition of waves occur and why does it happen?
Superposition happens when two or more waves pass through each other. At the instant the waves cross, the displacements of each combine.
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What is stated in the principle of superposition?
It states that that when two or more waves cross, the resultant displacement equals the vector sum of the individual displacements
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What is a stationary wave?
A wave that is produced by the superposition of two progressive waves with the same frequency or wavelength in opposite directions
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What is a node?
Point of minimum displacement on a stationary wave (antinode being the opposite)
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What is refraction?
When a wave changes direction as it enters a different medium
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What is diffraction?
When a wave changes speed as it passes through a gap
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Define coherence
Sources that have the same wavelength and frequency and a fixed phase difference between them
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What is meant by monochromatic light? Give an example of one
Light source with a single wavelength. An example is a laser.
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What pattern is created from a single slit using monochromatic light?
There is a bright central fringe (central max with alternating dark and bright firnges on either side) Pattern due to interference. Light fringes= integer wavelengths, constructive. Dark fringes= half wavelengths, destructive
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What was Young's double-slit experiment
The use of two coherent sources or the use of a single source with double slits to produce an interference pattern
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What is the refractive index of a substance s
n = c(air) / c(s)
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What is Snells law of refraction for a boundary?
n1sin(theta)1 = n2sin(theta)2
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Total internal reflection
sin(theta)C = n2/n1
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What is the critical angle?
The angle of incidence at which the angle of refraction is 90 degrees
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What is total internal reflection?
When all light is completely reflected back into a medium at a boundary with another medium, instead of being refracted. It only happens at angles of incidence greater than the critical angle.
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What are optical fibres?
Thin tubes of glass or plastic that can carry light signals using total internal reflection
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What is modal dispersion?
Caused by reflected light taking paths of different lengths in an optical fibre
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What is material dispersion?
Different wavelengths of light travelling at different speeds
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What is pulse broadening?
When signal in an optical fibre gets wider as it is transmitted due to dispersion (dispersion being a form of signal degradation that causes pulse broadening)
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What is absorption?
When some of the signals energy is taken in by the material the fibre is made of
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Other cards in this set
Card 2
Front
Point of maximum displacement on a wave from the equilibrium position
Back
Define amplitude
Card 3
Front
1/T (number of oscialltions per minute)
Back
Card 4
Front
the shortest distance between two particles that are oscillating in phase.
Back
Card 5
Front
The time taken for one complete oscillation of a particle in the wave.
Back
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