The relation V = IR is applicable to MCQ with Answer and Explanation

Explanation:
ν₀ ∝ φ. Double work function ⇒ double threshold frequency. Higher φ requires higher photon energy for emission. Memory tip: 'ν₀ = φ/h; larger φ ⇒ higher frequency needed'. Photoelectric effect relation frequently tested in competitive quantum physics sections.

Explanation:
Speed of sound in air v ∝ √T, where T is absolute temperature in Kelvin. T₀ = 0°C = 273 K, v₀ = 332 m/s. T = 27°C = 300 K. Thus v = v₀√(T/T₀) = 332 × √(300/273) ≈ 332 × √1.099 ≈ 332 × 1.048 ≈ 348 m/s ≈ 350 m/s. Approximate rule: speed increases by 0.6 m/s per °C rise, so 27×0.6≈16.2, 332+16.2≈348.2 m/s. Memory aid: 'v ∝ √T in Kelvin'. Such temperature-dependence problems test application of sound wave properties, common in competitive exams with emphasis on absolute temperature usage.

Explanation:
Audible range: 20 Hz to 20,000 Hz (20 kHz). Below 20 Hz infrasound, above ultrasound. This range decreases with age. Dogs can hear higher frequencies (ultrasonic whistles).