15. The frequency of light beam A is twice that of light beam B. The ratio EA/EB of photon energies is: (A) 1/2 (B) 1/4 (C) 1/3 (D) 2 (E) 8

10. In an oscillating series RLC circuit with R = 50 Ω, L = 20 mH and C = 2.0 μF, the maximum charge is stored on the capacitor at t = 0. Find the time required for the charge on the capacitor falling to 37% of its initial value. (A) 1. × 10⁻⁴ s (B) 2. × 10⁻⁴ s (C) 4. × 10⁻⁴ s (D) 6. × 10⁻⁴ s (E) 8. × 10⁻⁴ s