Question

Define the terms reflectance, absorptance and transmittance. How are they related? 

Answer 1

1) Reflectance – Ratio of amount of thermal radiations reflected by the body in a given time to total amount of thermal radiations incident on body It is represented by r, 

2) Absorptance – is the ratio of the amount of thermal to the total amount of thermal radiations incident on it. It is represented by a

3) Transmittance – It is the ratio of the amount of thermal radiations transmitted by body in a given time to the total amount of thermal radiations incident on the body in a given time. It is represented by t. 

Let Q = Amount of the radiations incident by the body in a given time 

Q₁ = Amount of thermal radiations reflected by the body in a given time. 

Q₂ = Amount of thermal radiations absorbed by the body in a given time. 

Q₃ = Amount of thermal radiations transmitted by the body in a given time

By definition,