Therefore, what happens, what I want to plot here this side; see this. If I call this to be s omega, what I want to plot is that s omega d omega must be equal to half A square. In other words, see all the waves… Let us say this is omega i. This area should represent energy of all the waves, which means this area should represent half A square. Then, how much is this value? This is of course… A i omega This is what we plot; this is what is called an energy spectrum. So, when I plot this… that means, on the vertical axis when I plot half A omega square by d omega; that is very important to have by d omega, because if you did not do, then if you add it all up; if I take 200, then if I add all the A square and if I take 300, then you will find the answer do not match. Remember that total area; see the total energy must be constant. Once again, I will give this demonstration here differently.