Question

The mode of heat transfer that requires no medium is:

• A. Conduction
• B. Convection
• C. Radiation
• D. Advection

Hint:

Radiation is the only mode of heat transfer that can occur in space where no medium is present—think of how sunlight reaches Earth!

Answer 1

The Correct Option is C

Step 1: There are three primary modes of heat transfer: conduction, convection, and radiation. Among these, conduction and convection require a medium (solid, liquid, or gas) for heat to transfer. 
Step 2: Radiation, however, is the transfer of heat energy via electromagnetic waves (primarily infrared), and it does not require any physical medium. This is how the Sun’s energy reaches the Earth through the vacuum of space. 
Step 3: Advection is a term used in fluid dynamics and refers to the bulk movement of heat or matter via a fluid flow, and thus it also requires a medium. 
Therefore, radiation is the only heat transfer mechanism that can operate in a vacuum. 

Why the other options are incorrect:

• (A) Conduction involves direct contact between molecules.
• (B) Convection requires fluid motion to carry heat.
• (D) Advection is a special case of convection and also needs a medium.