(b) Heat energy incident on the surface, Qi = 1000 J/m Coefficient of absorption, a = 0.8 coefficientof reflection, r = 0.1 Heat energy transmittedin 5 minutes, Qt = ? ∵ 1 = r + a + t ⇒ t = 1 - 0.1 - 0.8 = 0.1 Qt = Qi×t× T(t = coefficient of transmittance) Qt = 0.1 x 1000 x 5 = 500 J