Q1: The absorptivity of a grey body at a given temperature __________ with increasing wavelength of radiation.

ANS:D - may increase or decrease ; depends on the material

The absorptivity of a grey body at a given temperature generally remains constant with increasing wavelength of radiation. A grey body is defined as a surface that absorbs all radiation incident upon it, regardless of wavelength, and emits radiation according to Planck's law. The absorptivity of a grey body is independent of wavelength, meaning it absorbs radiation equally across the entire electromagnetic spectrum. Therefore, the correct option is: remains constant.