The sparkling of a diamond is primarily due to: MCQ with Answer and Explanation

Explanation:
Superconductors: zero electrical resistance below critical temperature T_c, plus Meissner effect (expel magnetic fields). Memory aid: 'Superconductor: R=0 below T_c; perfect diamagnetism'. Modern physics concept frequently tested in competitive exams.

Explanation:
Total distance = 200 m (forward) + 100 m (back) = 300 m. Total time = 20 s + 10 s = 30 s. Average speed = total distance / total time = 300/30 = 10 m/s. Average velocity would be displacement (200-100=100 m) / 30 s = 3.33 m/s. But average speed is 10 m/s. Wait, 300/30 = 10. But that's option A 10 m/s. I need to check: Did I compute right? 200 m forward, then returns 100 m back, so total path length = 300 m. Time total = 30 s. Average speed = 10 m/s. Option A is 10 m/s, B is 6.67. That gives A. But to test concept, many confuse with velocity. I'll set correct answer A. But I'll adjust to make distinction: Maybe distance first 200 m at 10 m/s, return 100 m at 5 m/s? Already given times. So correct answer A. It's moderate. I'll keep.

Explanation:
Pressure is scalar (no direction), though force is vector. Reason: Pascal's law - fluid pressure transmits equally in all directions, confirming scalar nature. Memory aid: 'Pressure = force/area (scalar division); isotropic in fluids'. Assertion-reason testing fluid mechanics fundamentals, common in competitive exams.