(a) Differentiate between interference and polarisation as applied to waves. (b) Mention two uses of polaroids
Question 1 Report
(a) Differentiate between interference and polarisation as applied to waves.
(b) Mention two uses of polaroids
Answer Details
(a) Interference vs polarisation
Interference is the superposition of two waves of the same frequency travelling in the same region, so that they reinforce one another (constructive interference) or cancel one another (destructive interference) depending on their path difference. It occurs in all types of waves (both transverse and longitudinal).
Polarisation is the restriction of the vibrations of a wave to a single plane containing the direction of travel. It occurs only in transverse waves, because it depends on the vibrations being at right angles to the direction of propagation. The fact that light can be polarised is direct evidence that light is a transverse wave.
(b) Two uses of polaroids
- In polaroid sunglasses to cut down glare (reflected, horizontally polarised light).
- In photographic filters and in liquid-crystal displays (LCDs) to control the intensity and plane of transmitted light; also in stress analysis of transparent materials.
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