Interference: Superposition Of Waves

Where                   ---------------- (5)

From eqn. (4), it is evident that the resultant of two waves is another wave having same frequency and direction of propagation, but with a different amplitude and phase.(Fig.1)

The energy associated with the resultant wave is proportional to the square of its amplitude.

The energy of individual waves is proportional is and respectively, where as the energy of resultant wave will be

i.e. the energy of the resultant wave is not just simple sum of energy of individual waves, but depends upon the difference in phases of the two waves, when the phase difference is 0 or even multiple of , the energy is maximum, whereas, if the phase difference is an odd multiple of , the energy is minimum. When the phase difference is an odd multiple of ,the energy is simply sum of the energy of two individual waves. The term is known as interference term. (Figure),