Deduce the expression for energy density.

Deduce an expression for the energy stored in a charged capacitor. Where the energy is stored ?

What are beats ? Deduce the expression for beat frequency.

The magnfication of a magnifier is M = q/p where the symbols carry their usual meaning. Deduce the expression for the magnification in terms of object distance,p,

Deduce an expression for the internal resistance of the cell.