Related Questions

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
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 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
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
Depending on the radiating properties, a body will be opaque when
A p = 0, x = 0 and a = 1
B p = 1, x = 0 and a = 0
C p = 0, x = 1 and a = 0
D x = 0, a + p = 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
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
A grey body is one whose absorptivity
A Varies with temperature
B Varies with wavelength of the incident ray
C Is equal to its emissivity
D Does not vary with temperature and. wavelength of the incident ray
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
Absorptivity of a grey body varies with the
A Wavelength of the incident ray
B Temperature
C Both A & B
D Neither A nor B

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