Three discs, A, B and C having radii 2m, 4m and6m respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are `300nm, 400nm` and `500 nm`, respectively. The power radiated by them are `Q_A, Q_B and Q_C` respectively
(a) `Q_A` is maximum (b) `Q_B` is maximum (c) `Q_C` is maximum (d) `Q_A = Q_B = Q_C`

Options

A. `Q_(A)=Q_(B)=Q_(C)`
B. `Q_(A)` is maximum
C. `Q_(B)` is maximum
D. `Q_(C)` is maximum

Answer

C

Explanation

`QpropAT^(4)orQpropr^(2)T^(4)`
and `lamda_(m)` T = constant
`thereforeTprop1/(lamda_(m))" "thereforeQpropr^(2)/((lamda_(m))^(4))`
`thereforeQ_(A):Q_(B):Q_(C)=2^(2)/(3)^(4):4^(2)/(4)^(4):6^(2)/(5)^(4)`
`=4/81:1/16:36/625`
`thereforeQ_(B)` is maximum.