Question

Heat transfer in vacuum occurs by:

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

Hint:

Remember:
- Conduction \(\rightarrow\) Solids (needs matter).
- Convection \(\rightarrow\) Fluids (needs moving matter).
- Radiation \(\rightarrow\) Vacuum or transparent media (does not need matter).

Answer 1

The Correct Option is C

Conduction needs atoms or free electrons passing vibrations and energy directly from one to the next, and convection needs bulk movement of a fluid carrying heat along with it, so both of these modes require some kind of physical material to work through. A vacuum, by definition, has essentially no atoms or molecules present at all, so neither of these mechanisms has anything to travel through. Radiation, however, works purely by electromagnetic waves being emitted by a hot surface and absorbed elsewhere, and these waves do not need any medium to carry them, they can cross completely empty space just as they cross air. This is exactly how the sun's heat reaches the earth across millions of kilometres of vacuum, with no conduction or convection possible along the way. So the correct choice is option (C).