Q.

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U1, at wavelength 500 nm is U2 and that at 1000 nm is U3. Wien’s constant, b=2.88×106nm K. Which of the following is correct           [2016]
 

1 U1>U2  
2 U2>U1  
3 U1=0  
4 U3=0  

Ans.

(2)

According to Wien's displacement law 

λm=bT=2.88×106nm K5760K=500 nm

Clearly from graph U2>U3 and U2>U1