Attempt any THREE :
Compare the rates of loss of heat by a black body at `627^(@)C` and `327^(@)C`, if tempreature of surrounding is `27^(@)C`.

Explanation

Given : `T_(1) = 627+ 273 = 900 K`
`T_(2) = 327 + 273 = 600 K`
`T = 27 + 273 = 300K`
`(R_(1))/(R_(2)) = ((900)^(4) - (300)^(4))/((600)^(4) - (300)^(4))`
`= ((9)^(4) - (3)^(4))/((6)^(4)- (3)^(4))`
`= (6561-81)/(1296 - 81)`
`= (6480)/(1215)`
`:. (R_(1))/(R_(2)) = 5.33`
`:. R_(1) :R_(2) = 5.33 : 1`