## Photon Energy Formula

A photon is defined as the quantum of electromagnetic radiation. The term quantum refers to the smallest elemental unit of a quantity. Hence, one quantum of electromagnetic energy is known as a photon.

A photon is characterized either by wavelength (Î») or an equivalent energy E.

The energy of a photon is inversely proportional to the wavelength of a photon.

The Photon energy formula is given by,

$E\,&space;=\,&space;\frac{hc}{\lambda&space;}$

Where

E = photon energy,

h = Planck’s constant (6.626Ã—10âˆ’34 Js),

c = speed of the light and

Î» = wavelength of the light.

Example 1

Determine the photon energy if the wavelength is 650nm.

Solution:

Given parameters are,

Î» = 650nm

c = 3Ã—108Ã—108m/s

h = 6.626Ã—10âˆ’34Ã—10âˆ’34Js

Photon energy formula is given by,

E = hc / Î»

E = 6.626Ã—10âˆ’34 Ã—3Ã—108 / 650Ã—10âˆ’9

= 19.878 x 1028 / 650Ã—10âˆ’9

= 0.030 x 10âˆ’17J

Example 2:

If the energy of a photon is 350Ã—10âˆ’10J, determine the wavelength of that photon.

Solution:

Given parameters are,

E = 350Ã—10âˆ’10J

c = 3Ã—108m/s

h = 6.626Ã—10âˆ’34Js

Photon energy formula is given by,

E = hc / Î»

So, Î» = hc / E

Â Â Â = 6.626Ã—10âˆ’34Ã—3Ã—108 / 350Ã—10âˆ’10

= 19.87 x 10-28 / 350 x 10âˆ’10

= 0.056 x 10-16 m