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
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
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
There are five persons sitting on a bench. Blue eyed lady sitting in the middle is my mother. At the extreme left, the man with grey hair is my maternal uncle. Lady sitting at the extreme right is having a pimple on her nose and is the wife of person who is sitting between blue eyed lady and grey haired man and has a pointed nose. A lady having marks on her face is the younger sister of the blue eyed lady and sitting on the remaining fifth place. The person having a pointed nose is the son of the blue eyed lady. What is the lady having marks on her face to the man sitting at extreme left ?
A Wife
B Maternal Aunt
C Sister
D Sister-in-law
Addition of small amount of __________ to grey cast iron is done to produce nodular grey cast iron.
A Manganese
B Phosphorous
C Magnesium
D Chromium
The percentage of carbon in grey iron castings usually varies between
A 0.5 to 1%
B 1.2%
C 2.5 to 4.5%
D 5 to 7%
A body is called grey if the monochromatic emissivity of the body is
A Zero
B Unity
C Same for all wavelengths
D Different for all wavelengths
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 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

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