Energy from Frequency Example Problem

Spectroscopy Example Problem

If you know the frequency of a laser beam, you can calculate the energy of a photon.
If you know the frequency of a laser beam, you can calculate the energy of a photon. Donald Iain Smith / Getty Images

This example problem demonstrates how to find the energy of a photon from its frequency.

Problem:

The red light from a helium-neon laser has a frequency of 4.74 x 10​14 Hz. What is the energy of one photon?

Solution:

E = hν where

E = energy
h = Planck's constant = 6.626 x 10-34 J·s
ν = frequency

E = hν
E = 6.626 x 10-34 J·s x 4.74 x 1014 Hz
E = 3.14 x -19 J

Answer:

The energy of a single photon of red light from a helium-neon laser is 3.14 x -19 J.