For an object other than a black body, it’s emissivity, e is                                

Related MCQs

• A burning wood in the fireplace has a surface temperature of 450°C. Assume the emissivity to be 1 and find the radiant emission of energy per unit area.
• 5 cm in diameter, through which 400 W of electric energy is deposited. Assume the surface emissivity to be 0.9 and neglecting incoming radiation, find the rod surface temperature?
• Reflective sheet materials used as thermal insulating material have                         reflectivity and                      emissivity.
• What relation between emissivity, e, and Absorptive Power, a, is given by Kirchhoff’s law?
• 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 embedded 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
• A faulty thermometer has its fixed points marked as 5° and 95°. The temperature of a body as measured by the faulty thermometer is 59°. Find the correct temperature of the body on a Celsius scale.
• As the wavelength of the radiation decreases, the intensity of the black body radiations                          
• A black body is defined as a perfect absorber of radiations. It may or may not be a perfect emitter of radiations.
• Electromagnetic wave theory of light could not explain Black Body radiations.
• 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