The SI unit of luminous intensity is MCQ with Answer and Explanation

Explanation:
sinθ_c = n₂/n₁ = 1/1.5 = 2/3 ⇒ θ_c = sin⁻¹(0.667) ≈ 42°. Total internal reflection condition. Memory tip: 'θ_c = sin⁻¹(1/n) for denser to air'. Optics calculation frequently tested in competitive exams with standard refractive indices.

Explanation:
KE = ½mv², ΔKE/KE = Δm/m + 2 Δv/v = 1% + 4% = 5%.

Explanation:
From floatation: ρ_wood/ρ_water = fraction submerged in water = 0.6. Thus ρ_wood = 0.6 g/cm³ (since ρ_water = 1 g/cm³). In new liquid (ρ_l = 0.8 g/cm³), fraction submerged f = ρ_wood/ρ_l = 0.6/0.8 = 0.75 = 75%. This uses the principle that fraction submerged equals density ratio. Memory aid: 'f = ρ_object / ρ_fluid'. Such comparative buoyancy problems test application of Archimedes' principle across scenarios, common in competitive exams. Always maintain consistent units (g/cm³ here simplifies calculation).