A 100 watt bulb emits monochromatic light of wavelength 400 nm . Calculate the number of photons emitted per second by the bulb.

Explanation

Power of the bulb = 100 watt = `100J s^(-1)`
Energy of one photon E = h v =` hc//lamda`
`=(6.626xx10^(-34)Jsxx3xx10^(8)"ms"^(-1))/(400xx10^(-9)m)`
`=4.969xx10^(-19)J`
Number of photons emitted
`(100Js^(-1))/(4.969xx10^(-19)J)=2.012xx10^(20)s^(-1)`