Q161
When absorptivity (α) = 1, reflectivity (ρ) = 0 and transmissivity (τ) = 0, then the body is said to be a
A.
Black body
AnswerB.
Grey body
C.
Opaque body
D.
White body
Answer: Option A
Solution
Answer: Option A
Solution:
A blackbody surface completely absorbs external irradiation, regardless of direction and wavelength distribution. Its surface absorptivity is always 1, so αλ = α = 1. The reflectivity of a blackbody is always zero.