A bulb emits light of wave length 396 nm. The bulb is rated as 100 watt and 10% of the energy is emitted as light. How many photons are emitted by bulb per second?
Energy of the bulb = 100 watt
= 100 J per second
Percentage of energy emitted as light = 10%
Energy emitted as light per second = 10 J
Energy of the photon = hν
=6.626×10−34×3×1083960×10−10
=0.5×10−18 J
Number of photons = total energy emitted per secondenergy of one photon=100.5×10−18
= 2×1019