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Modes of heat transfer: radiation and the need for a medium. Complete the statement about radiation heat transfer with respect to intervening media. Choose the option that correctly fills the blank.

Difficulty: Easy

requires a medium
does not require a medium
requires a very dense medium
requires only a transparent medium

Correct Answer: does not require a medium

Explanation:

Concept
Thermal radiation is electromagnetic energy exchange by emission/absorption of photons and does not require any material medium (it can propagate through vacuum). Conduction and convection, in contrast, require material media.

Final Answer
does not require a medium.

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