# A nitrogen gas laser pulse with a wavelength of 337 nm contains 3.83 mJ of energy. How many photons does it contain?

May 31, 2018

6.49 × 10^15\ "photons"

#### Explanation:

Energy of a single photon is

$\text{E" = "hc"/"λ}$

$\textcolor{w h i t e}{\text{E") = (6.626 × 10^-34\ "J s" × 3 × 10^8\ "m/s")/(337 × 10^-9\ "m}}$

color(white)("E") = 5.90 × 10^-19\ "J"

Number of photons in the laser is

$\text{n" = "Total Energy"/"Energy per photon}$

$\textcolor{w h i t e}{\text{n") = (3.83 × 10^-3 cancel"J")/(5.90 × 10^-19 cancel"J" "/photon}}$

color(white)("n") = 6.49 × 10^15\ "photons"