Q1: Absorptivity of a grey body varies with the

ANS:D - neither 'a' nor 'b'

1. Wavelength of the incident ray:
   • The wavelength of electromagnetic radiation (such as light or heat) refers to the distance between successive peaks (or troughs) of the wave. It is commonly denoted by the symbol λ and is measured in meters (m), though often expressed in nanometers (nm) or micrometers (µm) for convenience.
   • Different types of electromagnetic radiation have different wavelengths. For example, visible light has wavelengths ranging from approximately 400 nm (violet) to 700 nm (red), while infrared radiation has longer wavelengths beyond the red end of the visible spectrum.
   • The wavelength of the incident ray refers to the specific wavelength of the incoming radiation that interacts with a surface or material.
2. Temperature:
   • Temperature is a measure of the average kinetic energy of the particles (atoms or molecules) in a substance. It indicates how hot or cold a substance is relative to some reference point, typically measured in degrees Celsius (°C) or Kelvin (K).
   • At higher temperatures, the particles in a substance have greater kinetic energy and move more rapidly. Conversely, at lower temperatures, the particles have less kinetic energy and move more slowly.
   • Temperature plays a crucial role in determining the physical properties and behavior of materials. It affects phenomena such as thermal expansion, phase transitions (e.g., melting, freezing), and rates of chemical reactions.

• Wavelength of the incident ray: This refers to the specific wavelength (or range of wavelengths) of the incoming electromagnetic radiation that interacts with the surface of the grey body.
• Temperature: This refers to the temperature of the grey body itself. The temperature influences the energy distribution of the thermal radiation emitted by the body according to Planck's law, which can affect the interaction between the body and incident radiation.