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An ideal blackbody (emissivity ε = 1) at T = 1000 K emits how much (compared to a real surface at the same T with ε = 0.5)?
A{'text': 'Same', 'label': 'A'}
B{'text': 'TWICE as much — emissive power scales linearly with ε', 'label': 'B'}
C{'text': 'Half', 'label': 'C'}
D{'text': 'Four times', 'label': 'D'}
Answer & Solution
Correct answer: B. {'text': 'TWICE as much — emissive power scales linearly with ε', 'label': 'B'}
Real surface: E = εσT⁴. Blackbody (ε=1): E_b = σT⁴. Ratio = 1/ε. So if ε = 0.5, blackbody emits 2× more at the same temperature. Useful for designing real surfaces (low ε to retain heat, high ε to dissipate).
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