Q. A body at 500 K cools by radiating heat to ambient atmosphere maintained at 300 K. When the body has cooled to 400 K, the cooling rate as a percentage of original rate is about

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Q. Two spheres A and B of same material have radius 1 m and 4 m, and temperatures 4000 K and 2000 K respectively. Then the energy radiated by sphere A is

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Q. A small body has a total emissive power of 4.5 kW/m². Determine its surface temperature of maximum emission

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Q. A small black body has a total emissive power of 4.5 k W/m². In which range of the spectrum does this wavelength fall?

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Q. The sun emits maximum radiation of 0.52 micron meter. Assuming the sun to be a black body, Calculate the surface temperature of the sun

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Q. A furnace emits radiation at 2000 K. Treating it as a black body radiation, calculate the wavelength at which emission is maximum

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Q. Four identical pieces of copper painted with different colors of paints were heated to the same temperature and then left in the environment to cool. Which of the following paint will give fast cooling?

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Q. A surface for which emissivity is constant at all temperatures and throughout the entire range of wavelength is called

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Q. If radiant energy EB emitted by the black surface strikes the non-black surface. If non-black surface has absorptivity α, it will absorb how much radiations?

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Q. If two surfaces are at the same temperature, then the conditions correspond to mobile thermal equilibrium for which the resultant interchange of heat is zero are

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Q. The absorptivity of black body equals to

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Q. A diathermanous body

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Q. Choose the false statement

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Q. The emissivity and the absorptivity of a real surface are equal for radiation with identical temperature and wavelength. This law is referred to as

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Q. With an increase in wavelength, the monochromatic emissive power of a black body

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Q. The temperature of a solid surface changes from 27 K to 627 K. The emissive power changes would then confirm to the ratio

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Q. If the temperature of a hot body is increased by 50%, the amount of radiations emitted by it would increase by nearly

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Q. Consider two bodies, one absolutely back and the other non-black and let these be at same temperature. Which one of the following statement is correct?

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Q. When Stefan-Boltzmann law is applied to a black body, it takes the form

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Q. When the emissivity of non-black surface is constant at all temperatures and throughout the entire range of wavelength, the surface is called

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