Question

A 50 watt bulb emits monochromatic red light of wavelength of 795 nm. The number of photons emitted per second by the bulb is $x\times {10}^{20}$. The value of x is . (Nearest integer)
[Given: $h=6.63\times {10}^{-34}Js\text{and}c=3.0\times {10}^{8}m{s}^{-1}$]

Answer 1

$E=nh\nu =\frac{nhc}{\lambda }$
50 watt bulb emits 50 J energy per second.

$50=\frac{n\times 6.63\times {10}^{-34}\times 3\times {10}^8}{795\times {10}^{-9}}$

$n=\frac{50\times 795\times {10}^{-9}}{6.63\times {10}^{-34}\times 3\times {10}^8}$

$n=2\times {10}^{20}$
Value of x =2