Rayleigh scattering causes shorter blue wavelengths to scatter more effectively than longer red wavelengths when sunlight passes through the atmosphere, making the sky appear blue.

Period T = 2π√(m/k) = 2π√(5/200) = 2π√(1/40) = 2π × (1/(2√10)) = π/√10 ≈ π s (approximately).

Using P = V²/R, we get R = V²/P = (250)²/1000 = 62500/1000 = 62.5 Ω.

Due to refraction at the water-air interface, light bends as it exits water. This causes objects to appear at different positions and moving at different speeds than they actually are—an optical illusion, not actual motion change.

From orbital mechanics: v = √(GM/r). If r becomes 2r, then v_new = √(GM/2r) = v/√2. Velocity decreases by factor √2.

Energy of photon: E = hf = 6.63 × 10⁻³⁴ × 5 × 10¹⁴ = 3.315 × 10⁻¹⁹ J ≈ 2.07 eV. KE_max = E - φ = 2.07 - 2 = 0.07 eV. (Recalculation shows approximately 2.08 eV with more precision.)

Acoustic impedance (Z) = ρ × c, where ρ is density and c is sound velocity. SI unit is kg/(m²·s). It's crucial for understanding sound reflection and transmission.

Electric potential is defined as work done per unit charge. SI unit is Joule/Coulomb = Volt. Option D (Watt/Ampere) also equals Volt but option A is more fundamental.

Using lens formula: 1/f = 1/u + 1/v. 1/15 = 1/30 + 1/v gives v = 30 cm. When u = 2f, image forms at 2f with magnification -1 (same size, inverted, real).

At sunset, light travels through a longer path in the atmosphere. Shorter wavelengths (blue) scatter more (Rayleigh scattering), leaving longer wavelengths (red) to reach the observer.