Why does a change in impedance cause reflection?

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SUMMARY

A change in impedance causes reflection due to the principles of energy conservation and boundary conditions at the interface of differing impedances. When a wave encounters an interface with different impedances, not all energy is transmitted; the energy that is not transmitted is reflected back. This phenomenon is mathematically represented by the reflection coefficient formula R=(Z2-Z1)/(Z1+Z2), which quantifies the proportion of the wave that reflects at the boundary.

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

Claude.
 

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