Related Questions

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
In a city 40% of the people have black hair, 25% have black eyes and 10% have both black hair and black eyes. What percentage of the people in the city has neither black hair nor black eyes?
A 35
B 40
C 45
D 50
In a certain city 40% of the people have black hair, 25% have black eyes and 10% have both black hair and black eyes. What percentage of the people in the city have neither black hair nor black eyes?
A 35
B 40
C 45
D 50
In thermal radiation for a black body (where, ε is emissivity and α is absorptivity)
A α = 1; ε ≠ 1
B α ≠ 1, ε = 1
C α ≠ 1, ε ≠ 1
D α = 1; ε = 1
What is the absorptivity of a black body?
A 1
B 0
C 0.78
D 0.95
A perfect black body is a perfect __________ of radiation.
A Absorber
B Emitter
C Both A & B
D Neither A nor B
While the total emissivity of a perfect black body is unity, the same for a real body is
A 0
B 1
C > 1
D Between 0 and 1
The wavelength at which the maximum monochromatic emissive power occurs for a black body, is (where, T = absolute temperature of the black body)
A α.T
B α.$$\frac{1}{{\text{T}}}$$
C α.T4
D Independent of T
When α is absorptivity, ρ is reflectivity and τ is transmissivity, then for a diathermanous body,
A α = 1, ρ = 0 and τ = 0
B α = 0, ρ = 1 and τ = 0
C α = 0, ρ = 0 and τ = 1
D α + ρ = 1 and τ = 0
The sum of reflectivity and absorptivity for an opaque body is equal to
A 0.5
B 1
C 0
D 2

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