Polarization used in: MCQ with Answer and Explanation

Explanation:
In hot deserts, the sand heats the air immediately above it, making it less dense (optically rarer) than cooler air higher up. Light from a tall object (like the sky or a tree) traveling downwards passes from denser to rarer air layers, bending away from the normal. Eventually, the angle of incidence exceeds the critical angle, causing total internal reflection. The observer perceives this reflected light as a pool of water on the ground.

Explanation:
Weight = 50 N. Max static friction = μN = 0.4×50 = 20 N, insufficient to hold. So block slides down.

Explanation:
Fuse wire melts when current exceeds rating (Joule heating I²R), breaking circuit to prevent damage. Sacrificial overcurrent protection. Memory aid: 'Fuse = thermal cutoff; rated current slightly above normal'. Safety device function frequently tested in competitive electricity sections.