Practice question

**Photon energy** E = h f = h c/λ, momentum p = h/λ = E/c, power P = N E/t, N number of photons per second, wavelength λ = h c/E, for photon momentum 1.5×10⁻²⁷ kg·m/s frequency f = p c/h? Actually E = p c, f = E/h = p c/h =1.5×10⁻²⁷×3×10⁸/6.63×10⁻³⁴=6.79×10¹⁴ Hz, energy E= h f =4.5×10⁻¹⁹ J, for 5.0×10⁻¹⁹ J frequency f=E/h=7.54×10¹⁴ Hz. E = 3.0 × 1.6 × 10⁻¹⁹ = 4.8 × 10⁻¹⁹ J . For a photon, p = (E/c) = (4.8 × 10⁻¹⁹/3 × 10⁸) = 1.6 × 10⁻²⁷ kg m/s . Applying E = h f = h