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
Absorptivity of a body will be equal to its emissivity
A At all temperatures
B At one particular temperature
C When system is under thermal equilibrium
D At critical temperature
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
Emissivity of a white polished body in comparison to a black body is
A Higher
B Lower
C Same
D Depends upon the shape of body
The emissivity of a polished silver body is _________ as compared to black body.
A Same
B Low
C Very low
D High
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 absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.
A Increases
B Decreases
C Remains constant
D May increase or decrease ; depends on the material
Absorptivity and refletivity of a perfect black body are respectively
A 1 and 0
B 0 and 1
C 1 and $$\infty $$
D 0 and 0.5

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