When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,
Right Answer is:
α = 0, ρ = 0 and τ = 1
A body that allows heat radiation to pass through it is called a Diathermanous Body(diathermic or diathermal bodies).
A body’s behavior with regard to thermal radiation is characterized by its transmission τ, absorption α, and reflection ρ.
(A body with transmitivity 1, reflectivity 0, and absorptivity 0) Air, up to a certain extent can be considered as the diathermanous body because it transmits all the radiation without hearing itself.