Question

Find the number of photons absorbed per second by the surface.

• A. $2.52\times {10}^{18}$
• B. $2.52\times {10}^{19}$
• C. $2.52\times {10}^{-18}$
• D. $2.52\times {10}^{-19}$

Answer 1

The correct option is B $2.52\times {10}^{19}$

Power of the beam $P=10W$
Wavelength $\lambda =500nm=500\times {10}^{-9}m$
Energy of photon $E=\frac{hc}{\lambda }$
Number of photons absorbed per second $N=\frac{P}{E}=\frac{P\lambda }{hc}$
$\therefore$ $N=\frac{10\times 500\times {10}^{-9}}{6.62\times {10}^{-34}\times 3\times {10}^8}=2.52\times {10}^{19}$