Blackbody Color Change and Emissive Power – Rankers Physics

Heat Transfer - Radiation: Practice Problem & Solution

Assertion (A): Colour of a glowing black body changes on increasing its temperature. Reason (R): Spectral emissive power associated with each wavelength does not increase in same proportion on increasing temperature of the Black Body.  
(1) Both (A) & (R) are true and the (R) is the correct explanation of the (A)
(2) Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
(3) (A) is true but (R) is false
(4) Both (A) and (R) are false

Solution Explained:

To solve this problem, we apply the core principles of Heat Transfer - Radiation. Understanding the underlying formula is key to arriving at the correct answer below:

Assertion (A) is true due to Wien's displacement law; \(\lambda_{max}\) shifts to shorter wavelengths with increasing temperature. Reason (R) is true. Planck's law shows spectral emissive power increases disproportionately for different wavelengths with temperature. (R) explains (A) as this disproportionate increase causes the color shift.

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