A. 0
B. 1
C. > 1
D. Between 0 and 1
Related Mcqs:
- Absorptivity of a perfect black body is unity. Which of the following has maximum absorptivity ?
A. Aluminium foil
B. Refractory bricks
C. Iron plate
D. Coke breeze - A perfect black body is a perfect _____________ of radiation?
A. Absorber
B. Emitter
C. Both A. & B.
D. Neither A. nor B. - What is the emissivity of a black body ?
A. 0
B. 1
C. 0.5
D. 0.90 - A body is called grey if the monochromatic emissivity of the body is___________________?
A. Zero
B. Unity
C. Same for all wavelengths
D. Different for all wavelengths - Out of 100 kcal/second of incident radiant energy on the surface of a thermally transparent body, 300 kcal/second is reflected back. If the transmissivity of the body is 0.25, the emissivity of the surface will be_________________?
A. 0.35
B. 0.45
C. 0.55
D. 0.85 - The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)?
A. αT
B. α × 1/T
C. α T4
D. Independent of T - Absorptivity and reflectivity of a perfect black body are respectively _______________?
A. 1 and 0
B. 0 and 1
C. 1 and ∞
D. 0 and 0.5 - The absorptivity of a body is equal to its emissivity _________________?
A. At a particular temperature
B. For circular bodies
C. Under thermal equilibrium
D. None of these - With increase in temperature, the total emissivity of conductors____________________?
A. Increases
B. Decreases
C. Remain same
D. Decreases linearly - A _____________ surface has the maximum thermal emissivity out of the following ?
A. Black & smooth
B. Black & rough
C. White & smooth
D. White & rough
