1. The problem statement, all variables and given/known data Why is is that when we look in a mirror we expect to see a reflection equally as bright as the real image, but when we stand in front of a cliff and clap our hands we don't hear an echo as loud as the original sound? 2. Relevant equations [itex]R = (z2 - z1)/(z2 + z1)[/itex] 3. The attempt at a solution In a mirror, R is close to -1. For the cliff, R should still be pretty close to 1. For the echo spherical divergence must lead to a decrease in the volume heard after reflection but this does not seem to apply to the mirror. (Is this because we compare the mirrored image we see to the everyday image which has the same spherical divergence?). In reality, any cliff we have done this in front of is finite in size so not all sound energy is reflected.