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39 Cards in this Set
- Front
- Back
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Wave |
The oscillation of particles or fields |
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Progressive wave |
Carries energy from one place to another without transferring any material |
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Cycle |
One complete vibration of a wave |
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Displacement, x |
How far a point on the wave has moved from its undisturbed position |
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Amplitude, A |
The maximum magnitude of displacement |
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Wavelength |
The length of one whole wave cycle, distance between two adjacent points on a wave |
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Period, T |
the time taken for a whole cycle to complete or to pass a given point |
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Frequency, Hz |
The number of cycles per second passing a given point |
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Phase |
A measurement of the position of a certain point along the wave cycle |
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Phase difference |
The difference in phase angle between two waves or two points on a wave |
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Reflection |
the wave is bounced back when it hits a boundary |
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Refraction |
The wave changes direction as it enters a different medium, as a result of a change in speed |
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Transverse wave |
Oscillations are perpendicular to the direction of energy transfer |
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Longitudinal waves |
Oscillations are parallel to the direction of energy transfer |
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Polarised wave |
Oscillations are in one direction |
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Polarisation |
Filtering out the vibrations of a wave in all directions except one |
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Principle of Superposition |
when two or more waves cross, the resultant displacement equals the vector sum of the individual displacements |
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Constructive interference |
When two displacements add together to form a greater displacement |
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Destructive interference |
When two displacements add together and cancel each other out completely |
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In phase |
If two points are in phase they are both at the same point in the wave cycle. They have the same displacement and velocity. Phase difference of 0, 2π radians, 360°, a whole cycle |
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Antiphase |
If two points are in antiphase they are at opposite points in the wave cycle. Phase difference of 180°, π radians, half a cycle |
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Coherent sources |
Have the same wavelength and frequency, and a constant phase difference |
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Stationary/standing wave |
The superposition of two progressive waves with the same frequency and wavelength, travelling in opposite directions |
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Node |
Point of minimum or zero amplitude |
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Antinode |
Point of maximum amplitude |
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Diffraction |
Spreading out of waves |
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Monochromatic light |
All the light has the same wavelength and frequency |
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Intensity |
Power per unit area |
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(Absolute) Refractive index |
A measure of optical density of a material (how much it slows down light) |
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Relative refractive index |
The ratio of the speed of light in material 1 to the speed of light in material 2 |
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Angle of incidence |
The angle between the incoming light and the normal |
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Angle of refraction |
The angle between the refracted ray and the normal |
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Critical angle |
The angle of incidence which causes the light to be refracted along the boundary |
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Total internal reflection |
When the angle of incidence is greater than the critical angle, all the light is reflected back into the material |
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Optical fibre |
A very thin flexible tube of glass or plastic fibre that can carry light signals over long distances and round corners |
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Step-index optical fibre |
An optical fibre with a high refractive index surrounded by cladding with a lower refractive index to allow total internal reflection |
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Signal |
A stream of pulses of light |
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Modal dispersion |
Light rays enter the fibre at different angles and so take different paths, meaning they reach the end at different times |
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Material dispersion |
Light consists of different wavelengths that travel at different speeds, meaning different wavelengths reach the end of the fibre at different times |
