Radiation basics: Evaluate the statement “In a black body, all radiations are rejected.” Choose the correct assessment and reasoning.

Introduction / Context:
Blackbody radiation is a cornerstone concept in heat transfer and thermodynamics. It defines ideal absorption and emission characteristics and underpins Planck’s law and Stefan–Boltzmann law.

Given Data / Assumptions:

• “Black body” refers to an ideal surface with absorptivity equal to 1 at all wavelengths and directions.
• Thermal equilibrium concepts apply.

Concept / Approach:
A black body absorbs all incident radiation (it does not reflect or transmit). It also is the most efficient emitter at a given temperature. Therefore, the statement that it “rejects” all radiation is the opposite of the definition.

Step-by-Step Solution:

Verification / Alternative check:
Compare to “white body,” which reflects; black body exhibits the opposite behaviour.

Why Other Options Are Wrong:
Conditional “true” options conflict with the universal definition; wavelength or medium does not reverse the black body’s absorbing nature.

Common Pitfalls:
Confusing “black” with non-emitting; in thermal radiation, a perfect absorber is also a perfect emitter at that temperature.

Final Answer:
False