The expected answers are:

(a)In plane polarized light, the vibration of the particles are confined to a single plane while in ordinary light, the particles vibrate in all planes perpendicular to the direction of propagation of the wave.

(b)Any two correct uses of 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.

This question on plane polarization of light was not popular among the candidates. The few candidates that attempted the question also performed poorly.

In differentiating between plane polarized light and ordinary light, most of the candidates could not realize that in plane polarized light, the vibrations of the particles are confined to one plane while in ordinary light the particles vibrate in all directions.

ost of the candidates were, however, able to state the uses of polariod correctly.