How many photons per second emerge from a laser of power 2.00 mW with wavelength 605 nm?
(c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

Question

How many photons per second emerge from a laser of power 2.00 mW with wavelength 605 nm? (c = 3.00 × 10⁸ m/s, h = 6.626 × 10^-34 J ∙ s)

Quizplus · Accepted Answer

The energy of one photon is calculated using E = hc/λ. Substituting the given values, E = (6.626 × 10^-34 J∙s)(3.00 × 10^8 m/s) / (605 × 10^-9 m) = 3.29 × 10^-19 J. The number of photons per second is the power divided by the energy per photon: (2.00 × 10^-3 W) / (3.29 × 10^-19 J) = 6.09 × 10^15 photons/s.

How Many Photons Per Second Emerge from a Laser of Power