Question

Which of the following is/are correct about emissivity of a body?

• A. The emitted radiation varies continuously with wavelength
• B. The peak emissive power increases with temperature
• C. As the temperature of the body increases the wavelength at the point of peak emissive power reduces
• D. All of them

Answer 1

The correct option is D All of them

The emitted radiation varies continuously with wavelength. It can be explained by wein's displacement law, the wavelength, ${\lambda }_{max}$ for max emissive power from a black body is function of temperature.

${\lambda }_{max}\left(inmm\right)=\frac{2900}{T\left(inK\right)}$

From above expression, we can say that as temperature of body increases the wavelength at the point of peak emissive power reduces.

$E=ϵ\sigma T^4$ (emissive power)

$\Rightarrow E\alpha T^4$

As temperature increases peak emissive power increases.