A 25 watt bulb emits monochromatic yellow light of wavelength of `0.57mum` calculate the rate of emission o0f quanta per second.

Explanation

Energy of one photon
`=hv=(hc)/lambda=(6.626 xx 10^(-34) xx 3 xx 10^8)/(0.57 xx 10^(-6))`
`=3.487 xx 10^(-19)J`
`25W=25 J s^(-1)`
Number of photons emitted per second
`=(1)/(3.487 xx 10^(-19)) xx 25`
`=7.17 xx 10^(19)" photons s"^(-1)`