wave properties一問

Conditions:
During diffraction, consider ray as wave.
Both ray and wave can undergo reflection.

When wave is being diffracted, its energy disperse to all directions.
When part of the diffracted wave is reflected and received by a meter, because only part of energy of the ray is received by the meter, the meter will obviously show less energy is received than the whole ray without being diffracted, only reflected is received by the meter.
During diffraction, the ray diffracted to all direction, part of the energy of the ray may be lost.
During reflection, the reflected ray is not dispersed, but only travel in one direction.