Answer
$4.985\times 10^{-19}$ $photons/s$
Work Step by Step
In the previous part of this problem, we have estimated the radiative power ($P$) of the body:
$P=1.983\times 10^{-37}$ $W$
Now the energy of a single photon is given by
$E=hf$
or, $E=\frac{hc}{\lambda}$
Here, $\lambda=500\times 10^{-9}$ $m$
Therefore,
$E=\frac{6.63\times 10^{-34}\times 3\times 10^{8}}{500\times 10^{-9}}$ $J$
$E=3.978\times 10^{-19}$ $J$
$\therefore$ The rate ($R$) at which the photons are emitted from the given area is given by
$R=\frac{P}{E}$
$R=\frac{1.983\times 10^{-37}}{3.978\times 10^{-19}}$ $photons/s$
$R\approx 4.985\times 10^{-19}$ $photons/s$
