Compute the number of photons emitted per second by a 10 W sodium vapour lamp. Assume that 60 % of the consumed energy is converted into light. The wavelength of sodium light is 590 nm .

Step-by-step solution

Power of the lamp, P = 10 W Energy converted into light per second, E_ light = 60 100 10 = 6 J/s Wavelength of sodium light, = 590 nm = 590 10⁻⁹ m Energy of one photon is given by E = hc E = 6.63 10⁻³⁴ 3 10^8 590 10⁻⁹ 3.37 10⁻¹⁹ J Number of photons emitted per second, n = E_ light E n = 6 3.37 10⁻¹⁹ 1.77 10¹⁹