The process of heat transfer without any medium is MCQ with Answer and Explanation

Explanation:
Barometer measures atmospheric pressure. Mercury barometer (Torricelli) standard. Aneroid barometer. Manometer measures pressure difference. Hydrometer density. Lactometer milk purity.

Explanation:
pico = 10⁻¹². Femto = 10⁻¹⁵.

Explanation:
Critical angle θ_c for total internal reflection: sinθ_c = n₂/n₁, where n₁ > n₂. Here n₁=1.5 (glass), n₂=1 (air), so sinθ_c = 1/1.5 = 2/3 ≈ 0.6667 ⇒ θ_c = sin⁻¹(0.6667) ≈ 41.8° ≈ 42°. Memory aid: 'sinθ_c = 1/n for glass to air'. This calculation tests understanding of total internal reflection conditions, crucial for optics in competitive exams. Always ensure light travels from denser to rarer medium for TIR to be possible; otherwise, no critical angle exists.