Concepts of Physics

IIT JEE Physics (1978-2018: 41 Years) Topic-wise Complete Solutions

Resonance and Sound Waves


This demonstration illustrates the phenomenon of resonance.


a set of three pair of thin steel strips (e.g., hacksaw blade) of different lengths fixed to a wooden block. Metal strips of each pair are similar in colour and dimensions.



When a strip of one colour is plucked, only the other strip of the same colour starts vibrating whereas the strips of the other colour remain stationary showing that maximum energy is transferred when resonance occurs.

The natural frequency of metal strip is given by \(\nu=2\pi\sqrt{{k}/{m}}\), where \(k\) is stiffness (it is a material property equivalent to the spring constant) and \(m\) is the mass. The masses of strips of same length is equal and that of different length is unequal. Thus, natural frequencies of strips of same length is equal but that of different length is unequal.

This can also be used to demonstrate that waves travels through the solid (wooden base).