Practice question

**Frequency of light** remains unchanged when refracts from air into water because frequency determined by source, energy E= h f conserved, speed decreases v= c/n, wavelength decreases λ'=v/f= λ/n, energy of wave proportional to amplitude² not speed, intensity I =½ c ε₀ E₀², energy not depend on speed directly, when speed decreases amplitude may change but energy conserved, interference redistributes energy, total energy same, bright regions gain from dark. Speed in a medium v = (c/n) . Given n = 1.25 , c = 3.0 × 10⁸ m/s , v = (3.0 × 10⁸/1.25) = 2.4 × 10⁸ m/s . Using Δ = d sinθ,