The substance used as moderator in nuclear reactor must MCQ with Answer and Explanation

Explanation:
E ∝ ν: higher frequency ⇒ higher photon energy. Gamma rays (high ν) more energetic than radio waves (low ν). Memory aid: 'E = hν; blue light photons more energetic than red'. Quantum physics relation frequently tested in competitive exams.

Explanation:
T=2π√(L/g) => L = gT²/(4π²) ≈ (9.8×4)/(4×9.87) ≈ 1 m.

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.