ENERGY, FREQUENCY, AND WAVELENGTH

The energy contained in a single photon of EM energy can be found in terms of the frequency by this formula:
e = hf
where e is the energy (in joules) contained in a photon, f is the frequency of the EM wave disturbance (in hertz), and h is a constant known as Planck’s constant, approximately equal to 6.6262 × 10^-34.
If the wavelength λ (in meters) is known, and c is the propagation speed of the EM disturbance (in meters per second), then
e = hc/λ
This can be rearranged to determine the wavelength of a photon in terms of the energy it contains:
λ = hc/e
For EM rays in free space, the product hc is approximately equal to 1.9865 × 10^-25 because c is approximately equal to 2.99792 × 10⁸ m/s.