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

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Answer 1 · 2018-05-31T23:23:59

$6.49 × 10^15\ "photons"$

Energy of a single photon is

$"E" = "hc"/"λ"$

$color(white)("E") = (6.626 × 10^-34\ "J s" × 3 × 10^8\ "m/s")/(337 × 10^-9\ "m")$

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

Number of photons in the laser is

$"n" = "Total Energy"/"Energy per photon"$

$color(white)("n") = (3.83 × 10^-3 cancel"J")/(5.90 × 10^-19 cancel"J" "/photon")$

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