Dear @Fausto Galetto;

Something like the model in the attached picture.

Thanks

Dear Sarmad A. Jameel Altaie,

There are a lot of phenomena, which are described by wave equation. They are light, sound, gravity and even matter (in relativistic quantum mechanics, Klein–Gordon equation). Take any of them, and you will obtain good real life example.

Or, may be, I dont understand you?

Sincerely,

Daniil Stupin

Dear Sarmad, the wave equation is probably the most used PDE in practical applications. Waves exist in different media. Take geophysics as an example. There are surface and internal waves in the ocean, but there are also more complex nonlinear models comparing to PDE. There are wave processes in the Earth (seismic waves), acoustic waves in the air and water, electromagnetic waves in different media. Initial equations differ for each case, but wave equation can be derived in some approximation in most of the cases. It can be often solved analytically.