My dear friends, here today i will tell some good about this topic, 

By the matching of impedances we understand a selection of impedances  between different media in such a way tha maximum transfer of energy takes place from one medium to the other. This is essential requirement in many practical situations. Thus, impedance matching represents a very important practical problem via -a - vis energy transfer 

i) Long distance cables -  carrying energy have many lengths of wire joined end to end. These cables must be accurately matched at all joints, so that there is no wastage from energy reflection.

ii) A loudspeaker - has to be matched to the impedance of the power output of an amplifier by choosing the correct turns ratio on the coupling transformer. The amplifier gives us am amplified signal of the input signal (voice, music)

iii) The power transfer from a generator to ta circuit or electrical network is a maximum when the generator impedance is carefully matched with the circuit load.

The insertion of a coupling element between two mismatched impedances is of fundamental importance. It finds applications in many branches of physics, engineering. Such systems  also exist in optics. We describe the physics of impedance matching by taking the case of mechanical waves on a string, but the results can be taken as valid for all kinds of waves.

We know that at a joint of two different impedances, there is a definite reflection of incident energy of the wave. Such impedances are called mismatching.