Calculate the number of photons emitted per second by a 10 W sodium vapour lamp. Assume that 60% of the consumed energy is converted into light. Wavelength of sodium light = 590 nm.
energy used by lamp= 10 W.
Only 60% of energy given is converted into light
∴ 60% of 10 W=6 W is converted into light.
Energy of single photon=
.
=
No of photons (n) required to produce 6 W energy is
.
1