Chapter 11: Introduction to Modern Atomic Theory

The energy of this electromagnetic radiation, 7.95 x 10^-20 J, is a very small number.

But what is this the energy of?

To understand what this small value of energy is associated with we must understand that light is quantized...that is light is composed of 'units' of light, or (Einstein contributed this word) a photon of light.

A photon is a quantum of light, just as an atom s a quantum of matter. So 7.95 x 10^-20 J is the energy of a photon of light with a wavelength of 2500 nm.

However a mol of photons of this energy would contain,

7.95 x 10^-20 J x 6.02 x 10²³ photons = 48 kilojoules

which quite a bit of energy.

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