Question

An Argon laser gives off pulses of green light (wavelength = 514 nm). If a single pulse from the laser has a total energy of 10.0 mJ how many photons are in the pulse?

Answer 1

Answer:

$n=2.59\times 10^{16}$ photons

Explanation:

$E=n\times \frac{h\times c}{\lambda}$

Where,  

n is the number of photons

h is Plank's constant having value $6.626\times 10^{-34}\ Js$

c is the speed of light having value $3\times 10^8\ m/s$

$\lambda$ is the wavelength of the light

Given that, wavelength = 514 nm = $514\times 10^{-9}\ m$

Energy = 10.0 mJ = 0.01 J ( 1 mJ = 0.001 J )

Applying the values as:-

$0.01=n\times \frac{6.626\times 10^{-34}\times 3\times 10^8}{514\times 10^{-9}}$

$\frac{19.878n}{10^{17}\times \:514}=0.01$

$n=2.59\times 10^{16}$ photons