Why does a change in impedance cause reflection?

[lavster]

why does a change in impedance causes reflection? I know that R=(Z2-Z1)/(Z1+Z2), but what is it that makes the wave be reflected?

thanks

 

[Dale]

Basically it comes from energy conservation. At an interface of difference impedances not all of the energy will be transmitted beyond the interface. Since energy must be conserved, whatever is not transmitted must be reflected.

 

[Claude Bile]

An alternate, but equivalent explanation to Dale's, is that reflection occurs so as to satisfy the boundary conditions at the interface.

Claude.