State three methods of polarising an unpolarised... | WAEC SSCE - Physics - 2004

Question 1 Report

State three methods of polarising an unpolarised light

Answer

Three methods of producing (plane) polarised light from unpolarised light:

By reflection: reflecting light from a plane surface (e.g. glass or water) at the polarising angle (Brewster's angle) gives a completely plane-polarised reflected beam.
By selective absorption: passing light through a Polaroid (dichroic material) which transmits vibrations in one plane and absorbs those in the perpendicular plane.
By double refraction: passing light through a doubly refracting crystal such as calcite (Nicol prism), which separates the light into two plane-polarised beams.

(Polarisation by scattering, e.g. of sunlight by air molecules, is also accepted.)

Answer Details

Three methods of producing (plane) polarised light from unpolarised light:

By reflection: reflecting light from a plane surface (e.g. glass or water) at the polarising angle (Brewster's angle) gives a completely plane-polarised reflected beam.
By selective absorption: passing light through a Polaroid (dichroic material) which transmits vibrations in one plane and absorbs those in the perpendicular plane.
By double refraction: passing light through a doubly refracting crystal such as calcite (Nicol prism), which separates the light into two plane-polarised beams.

(Polarisation by scattering, e.g. of sunlight by air molecules, is also accepted.)

State three methods of polarising an unpolarised light