How do you calculate the energy of a photon of electromagnetic radiation?

Jul 11, 2014

You use either the formula $E = h f$ or E = (hc)/λ.

Explanation:

$h$ is Planck's Constant, $f$ is the frequency, $c$ is the speed of light, and λ is the wavelength of the radiation.

EXAMPLE 1

Calculate the energy of a photon of radiation whose frequency is 5.00 × 10^14 "Hz".

Solution 1

E = hf = 6.626 × 10^-34 "J"· color(red)(cancel(color(black)("s"))) × 5.00 × 10^14 color(red)(cancel(color(black)("s"^-1))) = 3.31 × 10^-19 "J"

The energy is 3.31 × 10^-19 "J".

EXAMPLE 2

Calculate the energy of a photon of radiation that has a wavelength of 3.3 µm.

Solution 2

E = (hc)/λ = (6.626 × 10^-34 "J"·color(red)(cancel(color(black)("s"))) × 2.998 × 10^8 color(red)(cancel(color(black)("m·s"^-1))))/(3.3 × 10^-6 color(red)(cancel(color(black)("m")))) = 6.0 × 10^-20 "J"

Here's a video on how to find the energy of a photon with a given wavelength.