A. Increases
B. Decreases
C. Remain constant
D. May increase or decrease; depends on the material
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 - The statement that “maximum wavelength of radiation is inversely proportional to the temperature” is ______________ law?
A. Stefan-Boltzmann’s
B. Planck’s
C. Wien’s displacement
D. None of these - 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 - The ratio of total radiating power to the absorptivity of the body depends upon the _____________ as per Kirchoff‟s law?
A. Wavelength of radiation
B. Nature of the body
C. Temperature of the body
D. None of these - The radiation heat flux from a heating element at a temperature of 800°C, in a furnace maintained at 300°C is 8 kW/m2. The flux, when the element temperature is increased to 1000°C for the same furnace temperature is_____________________?
A. 11.2 kW/m2
B. 12.0 kW/m2
C. 14.6 kW/m2
D. 16.5 kW/m2 - 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 - 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 - 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 - As per Kirchoff‟s law, the ratio of the total radiating power to the absorptivity of a body depends on the_______________?
A. Temperature of the body only
B. Wavelength of monochromatic radiation
C. Both A. and B.
D. Nature of material of body - The sum of reflectivity and absorptivity for an opaque body is equal to____________________?
A. 0.5
B. 1
C. 0
D. 2
