Answer
$1.03\times10^{16}$ photons
Work Step by Step
Total energy= $3.85\,mJ=3.85\times10^{-3}\,J$
Energy of one photon= $\frac{hc}{\lambda}$
$=\frac{(6.626\times10^{-34}\,J\cdot s)(3.00\times10^{8}\,m/s)}{532\times10^{-9}\,m}$
$=3.736466\times10^{-19}\,J$
Number of photons= $\frac{\text{Total energy}}{\text{Energy of one photon}}$
$=\frac{3.85\times10^{-3}\,J}{3.736466\times10^{-19}\,J}$
$=1.03\times10^{16}$
