Any transparent surface in practical is neither a perfect absorber of electromagnetic waves neither a perfect reflector. Generally all the transparent surfaces reflect some amount of irradiation and the other parts are absorbed and transmitted.
<u>That is given by as relation:</u>
where:
absorptivity which is defined as the ratio of the absorbed radiation to the total irradiation
reflectivity is defined as the ratio of reflected radiation to the total irradiation
transmittivity is defined as the ratio of total transmitted radiation to the total irradiation
The total amount of energy remains constant in an isolated system. It implies that energy can neither be created nor destroyed, but can be change from one form to another.
