Q. A body through which all the incident radiations passes, is called

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Q. Reflectivity is defined as

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Q. Of the radiant energy 350W/m² incident upon a surface 250W/m² is absorbed, 60W/m² is reflected and the remainder is transmitted through the surface. Workout the value for reflectivity for the surface material

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Q. A thin metal plate of 4 cm diameter is suspended in atmospheric air whose temperature is 290 K. This plate attains a temperature of 295 K when one of its face receives radiant energy from a heat source at the rate of 2 W. If heat transfer coefficient on both surfaces of the plate is stated to be 87.5 W/m 2 K, workout the energy lost by reflection

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Q. The value of reflectivity depends upon
(i) Body temperature

(ii) Wavelength of reflected radiation

(iii) Nature of surface of body

Identify the correct statement

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Q. When a surface absorbs a certain fixed percentage of striking radiation the surface is called

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Q. Which one is true regarding gases?

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Q. Thin glass plate is an example of

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Q. Radiant energy with an intensity of 800 W/m² strikes a flat plate normally. The absorptivity is thrice the reflectivity and twice the transmissivity. Determine the rate of reflection

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Q. Which one is true for opaque body?

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Q. Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of transmission

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Q. The absorptivity of a surface depends upon

(i) Direction of reflected radiation
(ii) Temperature of the surface
(iii) Composition

Identify the correct statements

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Q. What is the absorptivity of gray body?

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Q. A body that reflects all the incident thermal radiations is called a

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Q. Energy strikes a vertical hemispherical plate with an intensity of 640 W/m². The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of absorption

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Q. Let 220 W/m² of radiant energy is absorbed by a convex surface, 90 W/m² is reflected and 40 W/m² is transmitted through it. What is the value of absorptivity?

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Q. For a grey surface

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Q. Which quantity can be neglected for gases?

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Q. Absorptivity of a body is equal to its emissivity

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Q. Electromagnetic waves strikes a hot body maintained at 900 degree Celsius which has a reflectivity of 0.66 and a transmissivity of 0.022. Let the absorbed flux be 60 W/m². Determine the rate of incident flux

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