Question

A ruby laser delivers a 16.0-ns pulse of 4.20-MW average power. If the photons have a wavelength of 694.3 nm, how many are contained in the pulse

Answer 1

Answer:

The  value is  $n = 2.347 *10^{17} \ photons$

Explanation:

From the question we are told that

     The  amount of power delivered is  $P = 4.20 \ M W = 4.20 *10^{6} \ W$

      The  time taken is  $t = 16.0ns = 16.0 *10^{-9} \ s$

       The  wavelength is  $\lambda = 694.3 \ nm = 694.3 *10^{-9} \ m$

     

Generally the energy delivered is  mathematically represented as

     $E = P * t = \frac{n * h * c }{\lambda }$

Where  $h$ is the Planck's constant with value  $h = 6.262 *10^{-34} \ J \cdot s$

           c  is the speed of light with value  $c = 3.0*10^{8} \ m/s$

     

So  

    $4.20 *10^{6} * 16*10^{-9}= \frac{n * 6.626 *10^{-34} * 3.0*10^{8} }{694.3 *10^{-9}}$

=>    $n = 2.347 *10^{17} \ photons$