The unit of luminous flux is MCQ with Answer and Explanation

Explanation:
At 0°C, speed ~ 331 m/s. At room temperature (20°C) ~ 343 m/s, often taken as 340. Increases with temperature v ∝ √T. For many problems 340 is used, but at 0°C it's 331. So option A.

Explanation:
Impulse = F×Δt, unit N s, same as momentum kg m/s.

Explanation:
Lens maker's formula: 1/f = (μ_lens/μ_medium - 1)(...). In water, relative refractive index reduces, so power decreases, focal length increases. Glass in water behaves less converging.