Three discs A, B and C having radii 2m, 4 m and 6 m respectively are coated with carbon black on their outer surfaces. The wavelengths corresponding to maximum intensity are 300 nm, 400 nm and 500 nm respectively. The power radiated by them are `Q_(A),Q_(B)` and `Q_(C)` respectively :

Options

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

Answer

C

Explanation

`QpropAT^(4)`
Since `lamda_(m)T="Const"`.
`:.Qprop(A)/(lamda_(m)^(4))` or `Qprop(r^(2))/(lamda_(m)^(4))`.
`:.Q_(!):Q_(B):Q_(C)=(2^(2))/(3^(4)):(4^(2))/(3^(4)):(6^(4))/(5^(4))`
`=(4)/(81):(1)/(16):(36)/(625)`
Thus `Q_(B)` is maximum.
Correct choice is (c).