By conservation of energy, light energy incident on a dielectric (any transparent or translucent material) will automatically be equal to the sum of the amount of energy reflected and the amount of energy entering the medium.
Note: We cannot assume that the energy passing through is the same as the energy entering the medium as there will be scattering and light energy will be lost. The conservation of energy only applies at the boundary when the incident light hits the medium surface.
Relationships:
Energy incident = energy reflected + energy transmitted
Power incident = power reflected + power transmitted
Intensity incident = intensity reflected + intensity transmitted
