1. Light and Radiation

Electromagnetic waves    (4/4)

Interesting to note that the green curve in the graph shown on the previous page does not reflect the wave period T any more. Also, oscillations due to the wavelength λ in a graph of the wave against distance x would have dissapeared after distance-averaging.

Apparently, period and wavelength do not interfere in the energy flux of light and radiation. This is a consequence of taking the squares of E → or B → , or multiplying E → and B → , i.e., having the field quantities in squared terms only: subsequent averaging eleminates the information on wavelength and period in the argument of the sine term in the wave, and so also in the Poynting vector which corresponds to the intensity of light seen by the eye.

How is it then ever possible to see colours?

Indeed, it is not that easy to explain with electromagnetic theory the vision of colours. We need another physical model to get a better understanding of this phenomenon. This is the particle model of light: the photon model.
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colour and brightness in the sky

Colour and brightness in the sky.
You can test and deepen your knowledge on the topic of this chapter with the worksheet Light and Radiation. It can also be used as classroom task or homework assignment.