10-2.Heat Transfer question bank (Physics)

Three discs $x, y$ and $z$ having radii $2 \ m, 2 \ m$ and $6 \ m$ respectively are coated on their outer surfaces. If the wavelengths corresponding to the maximum power radiated by them are $3 \ \mu m, 4 \ \mu m$ and $5 \ \mu m$ respectively,then which of the following is true regarding the power radiated $(P)$?

$A$ black body radiates maximum energy at wavelength $\lambda$ at temperature $T_1$ and its emissive power is $E$. When the temperature of the body is changed to $T_2$, it radiates maximum energy at wavelength $\frac{2\lambda}{3}$, then the emissive power will become