The time taken by light to travel from Sun to Earth is approximately: MCQ with Answer and Explanation

Explanation:
H = I² R t = 25 × 10 × 120 = 30000 J = 30 kJ.

Explanation:
Total internal reflection (TIR) is exploited in optical fibers for light transmission with minimal loss (core-cladding interface). In diamonds, high refractive index (n≈2.4) gives small critical angle (~24°), so most light undergoes TIR, enhancing brilliance through multiple reflections. Memory aid: 'TIR applications: optical fibers (communication), diamonds (sparkle), prisms (binoculars)'. This application question tests optics uses, frequently appearing in competitive exams. Always link physical principles to technological applications; competitive exams emphasize practical relevance of theoretical concepts.

Explanation:
Convection involves fluid motion carrying heat. Conduction needs medium but no bulk motion; radiation needs no medium. Memory aid: 'Convection = fluid flow + heat transfer; e.g., boiling water, weather'. Definition-based question testing heat transfer modes, frequently examined in competitive exams to distinguish mechanisms.