Sun radiates thermal radiation with maximum intensity at the wavelength  λ=0.5 μm while its surface temperature is  6000 K. If sun cools down to a temperature where it emits only 81% of its present power, the maximum intensity will then be emitted at wavelength λ'  (in micro metre )is equal to  10=3.1622

1. When sun cools to the temperature T where it emits only 81% of its present radiating power, thenσT4=81100σ60004∵E=σT4   σ=5.67x 10-8 unit⇒T=0.96000 =0.95×6000=5700 K 2. By Wien’s displacement law,  λmT=constantHence if  λm is the required wavelength  λm5700=0.5×6000λm=60005700×0.5=1019=0.53 μm Therefore, the correct answer is 0.53