Rami Arieli: " The Laser Adventure" Chapter 2.2 page 3
Example 2.1: Visible Spectrum

The visible spectrum wavelength range is: 0.4 - 0.7 micron [mm] (400-700 [nm]).
The wavelength of the violet light is the shortest, and the wavelength of the red light is the longest. Calculate:

a) What is the frequency range of the visible spectrum.

b) What is the amount of the photon’s energy associated with the violet light, compared to the photon energy of the red light.

Solution to example 2.1:
The frequency of violet light:
The frequency of red light:
The difference in frequencies:
The energy of a violet photon:
The energy of a red photon:
The difference in energies between the violet photon and the red photon is:
2.15*10-19 [J]
This example shows how much more energy the violet photon have compared to the red photon.