Number of photons of equal energy emitted per second by a 6 mW laser source operating at 663 nm is _ _ _ _ . (Given : h =6.63 10⁻³⁴ ~J . s and c =3 10⁸ ~m / s )

Step-by-step solution

Power of laser: P = 6 mW = 6 10⁻³ J/s Energy of a single photon at wavelength = 663 nm: E = h = hc = 6.63 10⁻³⁴ 3 10^8 663 10⁻⁹ E = 6.63 3 663 10⁻³⁴⁺⁸⁺⁹ = 19.89 663 10⁻¹⁷ = 3 10⁻¹⁹ J Number of photons emitted per second: N = Total Energy per second Energy per photon = 6 10⁻³ 3 10⁻¹⁹ = 2 10¹⁶