A student claims that a blackened surface left in sunlight becomes hotter than a…
PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Modern Physics · Modern Physics
Problem
A student claims that a blackened surface left in sunlight becomes hotter than a polished metallic surface kept under identical conditions. Answer the questions that follow to examine this claim.
(i) Write the relation connecting absorptivity (a), reflectivity (r) and transmissivity (t) of any body for a given wavelength.
(ii) For an opaque body, show how the relation in part (i) is modified and explain the physical reason for the modification.
(iii) Using the ideas of part (ii), explain qualitatively why a perfect blackbody must have zero reflectivity and zero transmissivity.