Questions for Practice (Module 7)
Q.1  What is the wavelength for thermal and infrared radiation? 
Q.2  Define black body and grey body emphasising on the differences and similarity. 
Q.3  If a stainless steel body reflects 45% of the incident solar radiation, what will be the absorptivity and transmissivity? 
Q.4  What is Wein's law? 
Q.5  What is the practical advantage of studying radiation shield? 
Q.6  What is the difference between spectral emissive power and spectral radiation intensity? 
Q.7  A hollow sphere having 1 m of diameter is evacuated and heated to a interior surface temperature of 600^{o} K. If the sphere has a hole of 0.25 cm of diameter in the wall, how many watts of radiant energy is emitted from the hole. The inner surface of the sphere has an emissivity of (i) 0.9, and (ii) 0.4? 
Q.8  Find the view factor for the following geometry, all dimensions are in meter,

Q.9  A surface has a monochromatic emissivity of 0.2 for all the wavelengths less than or equal to 0.3micrometer and 0.85 for all the wabelengths greater than or equal to 3 micrometer. Find the total emissivity of the surface for a surface temperature of 1100^{o} K. Determine also the solar absorptivity of the surface. 