Q1: A body is called grey if the monochromatic emissivity of the body is

ANS:C - same for all wavelengths

When we say that a body is "grey" or has "grey behavior" regarding its emissivity, it means that the emissivity of the body is the same for all wavelengths of electromagnetic radiation. In other words, regardless of the wavelength of the radiation being emitted or absorbed by the body, the emissivity remains constant. This concept is often simplified in introductory physics and engineering contexts to help understand radiative heat transfer processes more easily. In practical terms, a grey body is a hypothetical idealization that simplifies the complex behavior of real materials when it comes to radiation. Real materials may have wavelength-dependent emissivities due to their composition, surface properties, and other factors. However, when dealing with simplified models or theoretical analyses, assuming a grey body can make calculations more manageable while still providing useful insights into radiative heat transfer phenomena.