A photon is characterized either by wavelength (λ) 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,
Where
E = photon energy,
h = Planck’s constant (6.626×10−34 Js)
c = speed of the light and
λ = wavelength of the light.
Example 1
Determine the photon energy if the wavelength is 650nm.
Solution:
Given parameters are
λ = 650nm
c = 3×108×108m/s
h = 6.626×10−34×10−34Js
Photon energy formula is given by,
E = hc / λ
E = 6.626×10−34 ×3×108 / 650×10−9
E = 19.878 x 1028 / 650×10−9
E = 0.030 x 10−17J
Example 2:
If the energy of a photon is 350×10−10J, determine the wavelength of that photon.
Solution:
Given parameters are,
E = 350×10−10J
c = 3×108m/s
h = 6.626×10−34Js
Photon energy formula is given by,
E = hc / λ
λ = hc / E
 λ = 6.626×10−34×3×108 / 350×10−10
λ = 19.87 x 10-28 / 350 x 10−10
λ = 0.056 x 10-16 m
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