Waves And Optics Flashcards
Uses of polarisation
Sunglasses - light can be polarised upon reflection
TV/ radio signals- alignment of aerials for transmission and reception
Conditions for the formation of a stationary wave
- two waves travelling in opposite directions
- coherent sources
- same type
- same frequency
- same polarisation (if transverse)
- perfect nodes form when the amplitudes are the same
How stationary waves differ from progressive waves
A stationary wave stores energy, it doesn’t transfer it
The amplitude is different at different points on the wave
All points between 2 nodes are in phase
Points separated by a node are 180 out of phase
Have nodes and antinodes
Harmonic rules
Number of harmonic = number of antinodes
Distance between nodes = lambda / 2
First harmonic frequency equation
fo = 1/2l root( T/ mu)
Maximally constructive interference
In phase
n lambda path difference
Maximum amplitude
Maximally destructive interference
Anti phase
(n + 1/2) lambda path difference
Minimum amplitude
Two source interference of light equation
w = lambda D/ s
W= fringe spacing Lambda= wavelength D = distance slits to screen S = slit spacing
Single slit width of central maximum
2D lambda / a
Diffraction grating equation
d sin(theta) = n lambda
Number of orders visible
n = d sin90/ lambda
Take integer part
Total number of visible bright spots: 2n + 1
Snell’s Law
n1 sinx1 = n2 sinx2
n(absolute refractive index) = c/cs
c = speed of light in vacuum cs = speed of light in substance
Critical angle
Sin(theta c) = n2/n1
Overcoming chromatic (material) dispersion
Use monochromatic radiation
Overcoming multi path (modal) dispersion
Fibre as straight as possible
Extremely thin fibre
High theta c
Reduce TIR
