Question

Nitrogen laser produces a radiation at a wavelength of $337\text{nm}$. If the number of photons emitted per second is $3.37\times {10}^{24}$, calculate the power of this laser.
(Given : $h=6.62\times {10}^{-34}\text{J.s}$)

• A. $4.5\times {10}^6\text{J}$
• B. $1.99\times {10}^6\text{J}$
• C. $3.3\times {10}^6\text{J}$
• D. $2.4\times {10}^6\text{J}$

Answer 1

The correct option is B $1.99\times {10}^6\text{J}$

Given:
$\text{Wave length}\left(\lambda \right)=337\text{nm}=337\times {10}^{-9}\text{m}$
$\text{Energy of one photon}=\frac{hc}{\lambda }$
$\text{Power of laser P}=\text{Energy emitted per second}=\frac{Nhc}{\lambda }$
$=\frac{3.37\times {10}^{24}\times 6.62\times {10}^{-34}\times 3\times {10}^8}{337\times {10}^{-9}}$
$=1.99\times {10}^6\text{J}$