Question: What is damping? Explain it as a gradual decrease in the amplitude of the oscillator.
Damping is any effect which reduces the amplitude of vibration of the oscillator.
Ideally, total energy of the oscillator should remain constant, and therefore, the SHM should continue forever. However, in real systems, the amplitude of oscillation gradually decreases with time until it dies out completely.
The reason is there are always forces which resist the motion of the oscillator. Due to this effect, the oscillator continuously works against these forces. As a result, the energy of the oscillator is continuously dissipated against these resistive forces which decreases the amplitude of oscillation.
As an example, consider the motion of a simple pendulum. As it moves, it suffers resistance from the air in its way, or friction at the pivot (point where it is suspended). The air resistance continuously decreases its K.E by decreasing its speed. In this way the P.E also decreases as during the course of motion of the pendulum, the K.E is converting to the P.E and vice versa. This gradually decreases its amplitude in every trip and finally it comes to stop.