The number of photons emitted per second by a 10 W sodium vapour lamp assuming that 90 % of the consumed energy is converted into light, is [Given, the wavelength of sodium light is 590 nm , Planck's constant, h = 6.63 × 10 - 34 J s ]

Step-by-step solution

Energy of photon E = h c λ = 6.63 × 10 - 34 × 3 × 10 8 590 × 10 - 9 = 6.63 × 3 59 × 10 - 18 Light energy produced per second = 90 100 × 10 = 9 W ∴ Number of photons emitted per second = 9 × 59 6.63 × 3 × 10 -18 = 2.67 × 10 19