$A$ star which appears blue will be

$A$ black body has a maximum wavelength $\lambda_{m}$ at a temperature of $2000 \ K$. Its maximum wavelength at $3000 \ K$ will be:

The temperature of a furnace is $2000^\circ C$ and the wavelength of maximum intensity in its spectrum is $4000 \ \mathring{A}$. If the wavelength of maximum intensity is $2000 \ \mathring{A}$, calculate the temperature of the furnace in $^\circ C$.

Three black discs $x, y, z$ have radii $1 \ m, 2 \ m$ and $3 \ m$ respectively. The wavelengths corresponding to maximum intensity are $200 \ nm, 300 \ nm$ and $400 \ nm$ respectively. The relation between emissive power $E_x, E_y$ and $E_z$ is:

Which graph represents the $v_m - T$ relationship for a black body,where $v_m$ is the frequency corresponding to the maximum energy emission and $T$ is the absolute temperature?

If the wavelengths of maximum intensity of radiations emitted by the sun and the moon are $0.5 \times 10^{-6} \ m$ and $10^{-4} \ m$ respectively,the ratio of their temperatures is: