Physics

Problem

Three identical metal plates are coated as follows and kept at the same temperature: P: matte black coating with

a_{\lambda}=0.95

Q: white paint coating with

a_{\lambda}=0.25

R: highly polished aluminium with

a_{\lambda}=0.05

Which plate will appear brightest (largest infrared intensity) on a thermal camera sensitive to wavelength

\lambda

? a) Plate R (polished aluminium) b) Plate P (matte black) c) All three plates appear equally bright d) Plate Q (white paint)