Related Questions

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 perfect black body is unity. Which of the following has maximum absorptivity?
A Aluminium foil
B Refractory bricks
C Iron plate
D Coke breeze
Total emissivity of polished silver compared to black body is
A Same
B Higher
C More or less same
D Very much lower
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
A perfect black body is a perfect __________ of radiation.
A Absorber
B Emitter
C Both A & B
D Neither A nor B
The emissivity for a black body is
A 0
B 0.5
C 0.75
D 1
What is the emissivity of a black body?
A 1
B 0
C 0.90
D 0.5
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

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