At a certain temperature for a given wavelength,the ratio of the emissive power of a body to the emissive power of a black body in the same circumstances is known as:

In which process is the rate of transfer of heat maximum?

There is a black spot on a body. If the body is heated and carried into a dark room,then it glows more than the rest of the body. This can be explained on the basis of:

Which of the following statements does not hold good for thermal radiation?

Heat radiations propagate with the speed of

If between wavelength $\lambda$ and $\lambda + d\lambda$,$e_\lambda$ and $a_\lambda$ are the emissive and absorptive powers of a body,respectively,and $E_\lambda$ is the emissive power of a perfectly black body,then according to Kirchhoff's law,which of the following is true?