Four pieces of iron heated in a furnace to different temperatures show different colours listed below. Which one has the highest temperature?

The black discs $x, y$ and $z$ 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

The maximum energy in thermal radiation from a source occurs at the wavelength $4000 \mathring A$. The effective temperature of the source is ....... $K$.

$A$ star which appears blue will be

$A$ body at $3000 \,K$ emits maximum energy at a wavelength of $9660 Å$. If the sun emits maximum energy at a wavelength of $4950 Å$, what would be the temperature of the sun (in $\,K$)?

Two stars emit maximum radiation of wavelength $3600 \ \mathring{A}$ and $4800 \ \mathring{A}$ respectively. The ratio of their temperatures is