A photon is an elementary particle, it has energy which is directly related to the photon’s wavelength which is inversely proportional to the energy, it means, the longer the photon’s wavelength, the lower its energy

**Photon energy = Plank’s constant * speed of light/photon’s wavelength**

The equation is:

E = hc / λ

Where:

E: photon’s energy

h: Plank’s constant

λ: photon’s wavelength

c: speed of light

### Photon Energy Formula Questions:

1) Calculate the energy of a photon which has a wavelength of 2.3 μm.

**Answer:**

We replaced the wavelength, Plank’s constant and the speed of light in the photon’s energy equation

E = (6.626 x 10^{-34} J.s)(3.0 x 10^{8} m/s) / 2.3 x 10^{-6} m

E = 8.64 x 10^{-20} J

2) Calculate the wavelength which has a photon with an energy of 6.0 x 10 ^{-20} J

**Answer:**

First we cleared the photon’s wavelength of the photon’s energy equation

λ = hc / E

Now we replaced the data

λ = (6.626 x 10^{-34} J.s)(3.0 x 10^{8} m/s) / 6.0 x 10^{-20} J

λ = 3.3 x 10 ^{-6} m