Polarization Flashcards
What is unpolarised light
completely random mixture of waves vibrating in all planes
What is polarised light
Transver wave motion in only one direction travel
What are the four ways that polarised light can be achieved and state whether it is artifically or naturally
Naturally
- polarisation by reflection
- polarisation by scattering
Artifically
- polarisation by transmission
- polarisation by refraction
Explain how polarisation by reflection takes place
Unpolarised light will resolve into 2 perpendicular components when incident on a flat surface. Occurs when reflected, direction of wave is perpendicular to refracted direction. Light that is specularly reflected is plane polarised in the plane of surface
What is Brewster’s angle
THe incident angle that causes plane-polarization
What is polarisation by scattering
Occurs when light hits any material and scatters. It results in scattered light can be either completely or partially polarised. Scattered light that is perpendicular to incident light is completely polarised. As angle varies, polarization decreases
What is polarization by transmission
Results from having a conducting material consiting of fine grid arranged horizontally or vertically. Light travels parallel to absorption axis is absorbed and light travelling parallel to transmission axis is transmitted.
What is a polaroid
A conducting material taht consist of fine grid arraganged either veritcally or horizontally
What are the two axis in a polaroid
Transmission axis
- light travelling parallel to this axis is transmitted
- perpendicualr to arrangement of molecules in polaroid
Absorption adxis
- light travlling parallel to this axis is absorbed
How is transmission applied
Polaroid sunglesses with vertical transmission axis does not transmit horizontally plane polarised light reflected at Brewster’s angle from flat horizontal surface
What is double refraction/ birefringence
Phenonmenon where objects are viewed through properly orientated, transparent, polished calcite crystal resulting in doubled images
What is a calcite crystal
A anisotropic material that results in different refractive index and absorption strengths in different direction, causing different polarisation component travling at different speed
How does light get polarized when it ether a calcite crystal
When light passes through a calcite crystal, it gets split into 2 serperate ray and either of the ray is plane polarised
How does light get polarized when it ether a calcite crystal
When light pases through a calcite crystal, it gets split into 2 serperate ray and either of the ray is plane polarised
How is polarization by refraction carried out
Occurs when light enters a anisotrophic material. Results in different absorption speeds and refractive indexes in different directions. Differnet polarization component travel at differnet speeds. Resulting in 2 rays, forming 2 images
