A bulb emits light of wavelength 198 nm. The bulb is rated as 100 watt and 10 % of the energy is emitted as light. The number of photons emitted per second is 10x. Take h=6.6×10−34. The value of x is
Energy of the bulb=100 watt=100J per second
Percentage of energy emitted as light = 10%
Energy emitted as light per second = 10 J
Energy of the photon = hν
=6.6×10−34×3×1081980×10−10
=1×10−18 J
Number of photons =Total energy emitted per secondEnergy of one photon
=1010−18 = 1019
Hence, the value of x=19