The expected answers are:
(a) In plane polarized light, the vibrations of the particles are confined to
a single plane while in ordinary light, the particles vibrate in many
planes
(b) Polaroid
e.g. - used in sun glasses to reduce the intensity of sunlight
- used to eliminate reflected light or glare
- sacharimetry/measurement of concentration of sugar solution
- (photo elastic) stress analysis
- production of three dimensional fil