Thermal radiation law identification: “The wavelength corresponding to maximum emissive power is inversely proportional to absolute temperature.” Does this statement describe Planck’s law?

Difficulty: Easy

Correct Answer: No

Explanation:


Introduction / Context:
Several named laws describe blackbody radiation. Correctly identifying which statement corresponds to which law helps avoid conceptual errors in heat transfer.



Given Data / Assumptions:

  • The quoted statement links peak wavelength and absolute temperature via an inverse relationship.
  • We compare with well-known radiation laws.


Concept / Approach:
Wien’s displacement law states: lambda_max * T = constant, meaning the wavelength at peak emission (lambda_max) is inversely proportional to temperature. Planck’s law, by contrast, gives the full spectral distribution of blackbody radiation intensity as a function of wavelength and temperature—not merely the location of the peak.



Step-by-Step Solution:

Identify the statement: “wavelength of maximum energy is inversely proportional to absolute temperature.”Recall Wien’s relation: lambda_max * T = b (constant) → lambda_max ∝ 1/T.Planck’s law provides E_lambda(T) using fundamental constants and exponential dependence; it does not simplify to the above proportionality.Therefore, the statement is Wien’s displacement law, not Planck’s law.


Verification / Alternative check:
Plotting blackbody spectra using Planck’s law shows peaks shifting with T such that lambda_max * T is constant, which is Wien’s result derived from Planck’s distribution.



Why Other Options Are Wrong:

  • Yes: Misattributes Wien’s law to Planck.
  • Only at very high temperatures / only for black surfaces: Wien’s law applies to ideal blackbodies across temperatures; emissive peaks for real surfaces follow similar trends but with emissivity effects.


Common Pitfalls:
Confusing names: Stefan–Boltzmann (total emission proportional to T^4), Wien (peak wavelength shift), Planck (full spectral law).



Final Answer:
No

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