What are stationary waves?

Answer

Stationary wave:
Whenever two progressive waves of the same wavelength and amplitude travel with the same speed through a medium in opposite directions and superpose upon each other, they give rise to what is caleld stationary or standing waves.
In stationary waves, there are certain points, where the amplitude is zero and strain is maximum. These point are known as nodes. Midway between these nodes, there is another category of points, where the amplitude is maximum and these strain is zero. These point are known as antinodes. In between the nodes and the antinodes, the amplitude lies between zero and maximum. These waves are scalled stationary waves, because there is no flow of energy along the wave. Like the progressive waves, stationary waves may be transver or longitudinal in nature.
Transerverse stationary waves. They are formed due to the superposition of two progressive transerve waves. For example, the stationary wave produced in the vibrating string of a sonometer in Melde's experiment.
Longitudinal stationary waves. They are formed due to the superposition of two progressive longitudinal waves. for example, the stationary wave formed in the vibrating air columns in the pipes, Kundt's tube and resonance apparatus.