Question

A certain laser transition emits $6.37\times {10}^{25}$ quanta per second per square meter. The power output in joules per square meter per second would be ($\lambda =632.8$ nm):

• A. $5\times {10}^{5}J{m}^{-2}se{c}^{-1}$
• B. $2\times {10}^{-3}J{m}^{-2}se{c}^{-1}$
• C. $9.2\times {10}^{-3}J{m}^{-2}se{c}^{-1}$
• D. $2\times {10}^{7}J{m}^{-2}se{c}^{-1}$

Answer 1

The correct option is D $2\times {10}^{7}J{m}^{-2}se{c}^{-1}$

Energy of a photon $=\frac{hc}{\lambda }[\lambda =632.8nm]$

$Power=\frac{Energy}{Areatime}=[\frac{hc}{\lambda }\times 6.37\times {10}^{25}]\frac{J}{m^{2}s}$

$=2\times {10}^{7}J/m^{2}s$