Q. Thermal radiation strikes a surface which has a reflectivity of 0.55 and transmissivity of 0.032. A quantity known as flux is found out to be 95 W/m². Determine the rate of incident flux.

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Q. What is the wavelength for visible light?

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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 absorption

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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/m² K, workout the reflectivity of the plate

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Q. On clear night there is radiation from earth’s surface to the space. On such a night, the water particles on the plant leaves radiate to the sky whose temperature may be taken as 200 K. The water particles receive heat by convection from the surrounding air, the convection heat transfer coefficient has a value of 30 W/m² K. If the water should not freeze, make calculations for the air temperature

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Q. “Isothermal furnaces, with small apertures, approximate a black body and are frequently used to calibrate heat flux gauges”. Chose the correct answer

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Q. “A surface element emits radiation in all directions, the intensity of radiation is however same in different directions. Choose the correct answer

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Q. The energy emitted by a black surface should not vary in accordance with

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Q. Likewise the amount of emitted radiation is strongly influenced by the wavelength even if temperature of the body is

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Q. A small body has a total emissive power of 4.5 kW/m². Determine the wavelength of emission maximum

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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 emissive ability of the sun’s surface at that temperature

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Q. The law governing the distribution of radiant energy over wavelength for a black body at fixed temperature is referred to as

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Q. The Planck’s constant h has the dimensions equal to

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Q. Planck’s law is given by

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Q. A furnace emits radiation at 2000 K. Treating it as a black body radiation, calculate the monochromatic radiant flux density at 1 micron m wavelength

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Q. A metal sphere of surface area 0.0225 m² is in an evacuated enclosure whose walls are held at a very low temperature. Electric current is passed through resistors imbedded in the sphere causing electrical energy to be dissipated at the rate of 75 W. If the sphere surfaces temperature is measured to be 560 K, while in steady state, calculate emissivity of the sphere surface

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Q. The Stefan-Boltzmann constant has units of

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Q. According to Stefan-Boltzmann law of thermal radiation

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Q. Calculate the radiant flux density from a black surface at 400 degree Celsius?

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Q. If the emitted radiant energy is to be doubled, to what temperature surface of black body needs to be raised? Take radiant flux density as 11631.7 W/m 2.

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