A lens of power +5 D has focal length MCQ with Answer and Explanation

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.

Explanation:
A Wheatstone bridge circuit consists of four arms with resistances P, Q, R, S and a galvanometer in the middle. It is balanced when no current flows through the galvanometer arm. This happens exclusively when the potentials at the two ends of the galvanometer are equal, meaning the potential difference across it is exactly zero (P/Q = R/S).

Explanation:
While James Clerk Maxwell predicted electromagnetic waves mathematically, it was the German physicist Heinrich Hertz who successfully built the first spark-gap transmitter in 1887. He physically generated and detected radio waves in his laboratory, proving Maxwell's theories right. The SI unit of frequency, the Hertz (Hz), is named in his absolute honor.