Waves Flashcards
Define What total internal refraction is
The angle of incidence required for a total internal refraction
Are mechanical waves longitudinal or transverse
Transverse
Are electromagnetic waves transverse or longitudinal
Transverse
Equivalent name of peaks and troughs within a longitudinal wave
Compressions and Rarefactions
Define Polarisation
When fields of an electromagnetic wave only oscillate in one direction
Explain how a polarisation filter works
Light is polarised when it passes through a polarising filter. The filter only allows through electric field oscillations in one plane because the filter absorbs energy from oscillations in all other planes.
What happens when light passes through 2 polarising filters at different angles
No incident wave gets through
If an incident ray moves towards the normal at the surface boundary what does this tell us about the refractive index of both substances
n(1) < n(2)
If a ray of light slows as it enters a boundary air to substance what does this tell you about the substance’s refractive index?
Refractive index > 1
What is an optical fibre
A thin glass or plastic fibre that transmits light, trapped inside the fibre by repeated total internal reflection
What is a step index optical fibre
An optical fibre with a uniform refractive index at the core and a smaller uniform refractive index for the cladding
What is Material Dispersion
The spreading of a signal through an optical fibre caused by different wavelengths of light in the signal travelling at different speeds. This results in pulse broadening.
What is pulse broadening
Occurs when the duration of a pulse increases as a result of light dispersion in an optical fibre
What is Modal dispersion
The spreading of a signal caused by rays inside the fibre taking slightly different paths. This leads to pulse broadening
What is light absorption
When energy from a certain wavelength of light is absorbed strongly by certain materials
True or false: An optical fibre commonly has a high absorption rate
False
What is the difference between material and modal dispersion
Material dispersion occurs due to varying frequencies of light travelling at different speeds, causing a variation of refractive index
Modal dispersion is when rays inside an optical fibre simply take different routes through a fibre causing variations in path distance
What is superposition
When two waves of the same type meet at the same point and overlap so that their total displacement is the vector sum of the displacement of each wave
What is wave interference
The superposition of waves from two coherent sources of waves. Interference is constructive if waves are in phase or destructive if they are antiphase
What are coherent waves
When two waves are coherent, the have a FIXED PHASE DIFFERENCE and have the SAME FREQUENCY.
What is seen on the screen of the double slit experiment
A series of fringes maxima (where constructive interference has occurred) and minima (where destructive interference has occurred)
How is a stationary wave created
Stationary waves are created when two progressive waves of the same frequency and amplitude moving in opposite directions superpose
What is the difference between a node and an antinode on a stationary wave
A node is a point of zero amplitude and an antinode is a point of maximum amplitude on a stationary wave
