A blue lamp mainly emits light of wavelength `4500Ã…`. The lamp is rated at 150 W and `8%` of the energy is emitted as visible light. The number of photons number of photons emitted by the lamp per second is

Explanation

A `150 W` bulb emits `150 J` of energy per second .The energy emitted by the bulb as light is `150 xx (8)/(100) = 12 J`
Let the bulb emit n potons per second
`E = nhv = (nhv)/(lambda)`
`:. N = (E xx lambda)/(c xx h)`
`= (12 J xx 45000 xx 10^(-19)m)/(3 xx 10^(8) ms^(-1) xx 6.63 xx 10^(-34) Js)`
`= 2.715 xx 10^(19)`