The mechanism of heat transfer from one point to another through the vibration of the molecules of the medium is

1. Analyze the question The question asks which mode of heat transfer works through the vibration of molecules of a medium. Two clues matter here:

• A medium is needed, so the heat cannot travel through empty space.
• The molecules vibrate, passing energy to their neighbours, rather than moving from place to place.

2. Explain the concepts

| Mode | How it works | Medium needed? | |---|---|---| | Conduction | Vibrating molecules pass kinetic energy to neighbouring molecules. The molecules stay in place. Common in solids. | Yes | | Convection | Bulk movement of the fluid (liquid or gas) carries heat, as in rising warm air or boiling water. | Yes (fluid) | | Radiation | Electromagnetic waves (infrared) carry heat. | No | | Diffusion | Particles spread from high to low concentration. It is not a heat transfer mode. | Yes |

3. Step-by-step solution

• Radiation is ruled out because it needs no medium and involves no molecular vibration.
• Convection is ruled out because the molecules themselves move in bulk and carry the heat with them, rather than just vibrating.
• Diffusion is ruled out because it is the mixing of particles, not heat transfer through vibration.
• Conduction fits. Heat moves from the hot end to the cold end as vibrating molecules pass energy to the molecules next to them. One example is a metal spoon getting hot at the handle when its tip is in hot soup.

4. Answer The correct option is B. conduction.

5. Exam tip Link each mode to a key word:

• Conduction → Contact/vibration (solids)
• Convection → Currents (fluids)
• Radiation → Rays (no medium needed)

Also note that option A is misspelt in the question ("covection"), so read all options carefully in the exam.