The least count of a screw gauge is 0.001 cm. The reading of a measurement is 0.250 cm. How many significant figures does it have? MCQ with Answer and Explanation

Explanation:
A rainbow is formed by sunlight interacting with water droplets. As light enters the droplet, it undergoes refraction and dispersion (separating into colors). The light then strikes the back of the droplet and undergoes total internal reflection. Finally, it undergoes a second refraction as it exits, spreading the spectrum out for the observer to see.

Explanation:
During phase change (melting), heat energy (latent heat) is used to overcome intermolecular forces, increasing potential energy while kinetic energy (hence temperature) remains constant. Temperature reflects average kinetic energy; since it doesn't change, kinetic energy is unchanged. The energy breaks hydrogen bonds in ice, allowing molecules to move freely in liquid. Memory tip: 'Latent heat changes state, not temperature'. This conceptual question tests understanding of microscopic interpretation of phase changes, frequently examined in competitive tests to assess depth beyond formula recall.

Explanation:
Volume V = (4/3)πr³, so ΔV/V = 3 Δr/r. Percentage error in volume = 3 × 2% = 6%.