Answer:
(a) Eₐ = 6.36 J/s
(b) Eₐ = 4.64 J/s
Explanation:
Stefan-Boltzmann law: States that the total energy per second radiated or absorbed by a black body is directly proportional to the absolute temperature.
Using, Stefan-Boltzmann equation
Eₐ =eσAT⁴ ................ Equation 1
where Eₐ = Radiant energy absorbed per seconds, e = emissivity, σ = stefan - boltzman constant, A = Surface area. and T = temperature in kelvin
(a) Where e = 0.89, σ = 5.67 ×10⁻⁸ watt/m²/K⁴, A = 140 cm² = 140 cm²(m²/10000cm²) = 0.014 m², T = 35 °C = (35 + 273) K = 308 K.
Applying these values in equation 1 above,
Eₐ = 0.89 × 5.67 ×10⁻⁸ × 0.014 × (308)⁴
Eₐ =6.36 J/s
(b) when e = 0.65,
∴ Eₐ = 0.65 × 5.67 × 10⁻⁸ × 0.014 × (308)⁴
Eₐ = 4.64 J/s
