Waves Flashcards
What is a progressive wave?
A progressive wave transfers energy without transferring material
What is amplitude
A waves maximum displacement from the equilibrium position
What is frequency
The number of complete oscillations passing through a point per second
What is wavelength
The length of one whole oscillation
What is phase
The position of a certain point on a wave cycle
What is phase difference
How much a particle/wave lags behind another particle/wave
If two points are in phase what characteristics are the same?
They will have the same displacement and velocity- this is caused by having the same frequency and wavelength
What are the properties of a transverse wave?
particles traverse at right angles to the direction of energy transfer
What are the properties of a longitudinal wave?
Oscillation of particles is parallel to the direction of energy transfer
What is superposition
Where the displacements of two waves are combined as they pass each other, with the result being a vector sum of each waves displacement
What is constructive interference?
When two waves have displacement in the same direction
What is destructive interference?
When one wave has a positive displacement and the other has negative displacement
What is total destructive interference?
When the waves have equal and opposite displacement total destructive interference occurs
How is a stationary wave formed?
When 2 progressive waves that are travelling in opposite directions with the same frequency, wavelength and amplitude superpose
When does refraction occur?
When a wave enters a different medium causing it to change direction, either towards or away from the normal.
What is snells law?
n1sin0 = n2sin0
If a ray of light travels into a more optically dense medium will the light beam move towards or away from the normal.
Bend towards the normal.
When does TIR occur?
Total internal reflection occurs when the angle of incidence is greater than the critical angle and the incident refractive index is greater than the refractive index of the material at the boundary.
What its absorption?
Where part of the signals energy is absorbed by the fibre, reducing the amplitude of the signal which can lead to the loss of information.
What is dispersion?
Dispersion causes pulse broadening, which is where the received signal is broader than the original transmitted signal.
What is modal dispersion?
When light rays enter the fibre at different angles this causes the rays to take a different amount of time to reach the end of the fibre causing pulse broadening.
What is material dispersion?
When lights of different wavelengths are sent along a fibre, they travel at different speeds along the fibre leading to pulse broadening.
How can absorption and dispersion be reduced?
By using an optical fibre repeater, which regenerates the signal during its travel to its destination
