note that the reflected pulse has a smaller amplitude than the incident pulse. in section 16.5, we show that the energy carried by a wave is related to its amplitude. according to the principle of the conservation of energy, when the pulse breaks up into a reflected pulse and a transmitted pulse at the boundary, the sum of the energies of these two pulses must equal the energy of the incident pulse, because the reflected pulse contains only part of the energy of the incident pulse, its amplitude must be smaller