L11 Polarization Flashcards
1
Q
define polarisation
A
the process of transforming unpolarised light into polarised light
2
Q
what is unpolarised light
A
transverse (light) waves vibrating in ALL planes. light waves known to vibrate in a multitude of direction
3
Q
what is polarised light
A
transverse waves vibrating in only ONE plane
4
Q
state 4 methods of polarisation
A
transmission, reflection, refraction, scattering
5
Q
explain polarisation by transmission
A
- use polariser filters: vibrations parallel to transmission axis is transmitted, those parallel are absorbed
- polaroid: 50/50 (1 trans axis, 1 ab axis)
- cross polaroid: 0 transmitted (2 trans axis)
- law of malus: iTrans = iMax (50%) x cos^2Tether
6
Q
explain polarisation by reflection
A
- wholly/partially polarised by reflection by non conductors
- dependent on (1) angle light hits surface (2) material of surface
- (1) when REFRAacted light PERPENdicular to REFLEcted light, TOTALly plane-polarised
- brewster: tanB = nā (incident) / n
- (2) metallic surfaces reflected unpolarised light, non metallic (snow, water) reflect some degree of polarised light (in plane parallel to surface)
7
Q
explain polarisation by refraction
A
- double refraction/birefringence: rays divide and bend into 2 in diff direction due to (anisotropic materials) diff struc in diff directn, diff RI in diff directn
- light associated with each image is plane polarised perpendicular to that of the other
8
Q
polarisation by scattering
A
- wholly/partially polarised
- wholly=skylight at 90deg to sun
