Q. If a black body at 1000 K and a gray body at 1250 K emit the same amount of radiation, what should be the emissivity of the gray body?

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Q. The radiant heat transfer from a plate of 2.5 cm² area at 1250 K to a very cold enclosure is 5.0 W. Determine the emissivity of the plate at this temperature

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Q. A 100 W light bulb has a tungsten filament (emissivity = 0.30) which is required to operate at 2780 K. If the bulb is completely evacuated, calculate the minimum surface area of the tungsten filament

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Q. For a hemisphere solid angle is measured as

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Q. A gray body (E = 0.8) emits the same amount of heat as a black body at 1075 K. Find out the required temperature of the gray body

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Q. The heat energy absorbed by a known area in a fixed time is determined with the help of an instrument called

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Q. The value of solar constant varies between

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Q. The total amount of heat energy received by the sphere of radius r is

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Q. Amount of heat energy radiated by unit surface of the sun in the same time workout as
Take, R = mean distance of earth from the sun and r = radius of sun

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Q. Temperature of sun can be workout from

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Q. The temperature of the photosphere, referred to as the effective temperature of the sun, is usually taken as

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Q. The approximate distribution of the flow of sun’s energy to the earth’s surface is

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Q. The solar radiation that is felt at the earth’s surface includes

(i) Direct radiation that has passed through the atmosphere

(ii) Diffuse radiation from the sky

(iii) Absorbed radiation from the water

Identify the correct statement

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Q. When the sun lies at a mean distance from the earth, the heat flux from the sun to the outer edge of the atmosphere has been found to be

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Q. Which one is having highest value of solar absorptivity?

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Q. What is the value of solar absorptivity for aluminum foil?

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Q. What is the value of solar absorptivity for polished copper?

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Q. Which one is having lowest value of solar absorptivity?

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Q. What is the value of solar absorptivity for polished stainless steel?

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Q. What is the value of solar absorptivity for white marble?

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