I was going through the texts of my book and read that intensity of a wave is proportional to its amplitude squared. I don't know how this relation came?
I thought for it but didn't come with any solution. My intuition was this :
Amplitude of fields is proportional to the energy supplied to an oscillating charge because the more energy is given the more change should come. Also the more energy is given, the more energy will be released. From the above statements we can conclude that energy released per unit time and per unit area i.e. intensity must be proportional to the amplitude not its square.
What's wrong in the this? Can the well known relation be proved?