Photon energy

The Energy of a Photon calculator computes the energy of a photon based on the wavelength (λ), Plank's Constant (h), and the speed of light (c)

INSTRUCTIONS: Choose units and enter the following:

• (λ) Wavelength of light

Energy of a Photon(E): The calculator returns the energy in Joules.  However, this can be automatically converted to compatible units via the pull-down menu.

The Math / Science

Certain conditions make it possible to describe light as a particle, or photon^[1]. The energy of each photon of light corresponds to a specific frequency. This relationship is described by Planck's equation:

          E=(h•c)/λ

where

• E is the energy of the photon
• h is Planck's constant 
• c is the speed of light ( 2.998 × 10⁸ m/s)
• λ is the wavelength of the light

Example

You see a green light with a wavelength of 530nm. Calculate the energy, in joules, associated with a photon of this light.

First, we define our variables:

• λ = 530nm = 5.3 x 10^-7 m
• h = 6.626 × 10 ^-34 joules*s
• c = 2.998 × 10⁸ m/s

E=(hc)/λ

Next, we substitute in our values and calculate the energy:

E = (6.626 × 10 ^-34 joules*s)(2.998 × 10⁸ m/s) / (5.3 x 10^-7m)

E = 3.748 x 10^-19 joules

References

Whitten, et al. "Chemistry" 10th Edition. Pp. 137

Chemistry Worksheet: Planck's Equation

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