According to Kirchoff's law, the ratio of emissive power to absorptivity for all bodies is equal to the emissive power of a

A Grey body
B Brilliant white polished body
C Red hot body
D Black body

Correct Answer: Black body

Kirchhoff's law states that the emissivity and the absorptivity of a surface at a given temperature and wavelength are equal. The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body.
This statement is known as Kirchhoff's law.
Bissoy MCQ
#Mechanical Engineering #Heat And Mass Transfer

Related Questions

The ratio of total radiating power to the absorptivity of the body depends upon the __________ as per Kirchoffs law.
A Wavelength of radiation
B Nature of the body
C Temperature of the body
D None of these
As per Kirchoffs 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 ratio of the total emissive power to the absorptivity for all bodies is same at ther-mal equilibrium. This is __________ law.
A Kirchoffs
B Planck's
C Wien's displacement
D Stefan-Boltzman
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
Newton's law of Collision of elastic bodies states that when two moving bodies collide each other, their velocity of separation
A Is directly proportional to their velocity of approach
B Is inversely proportional to their velocity of approach
C Bears a constant ratio to their velocity of approach
D Is equal to the sum of their velocities of approach
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 sum of reflectivity and absorptivity for an opaque body is equal to
A 0.5
B 1
C 0
D 2
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
The emissive power of a body depends upon its
A Temperature
B Wave length
C Physical nature
D All of the above
Which one gives the monochromatic emissive power for black body radiation?
A Planck's law
B Kirchhoffs law
C Wien's law
D Stefan-Boltzman law

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