When an iron rod is heated, the variation of colour from dull red to white can be explained by

Two stars $P$ and $Q$ are observed at night. Star $P$ appears reddish while star $Q$ is white. From this we conclude:

The plots of intensity $(I)$ versus wavelength $(\lambda)$ for three black bodies at temperatures $T_1, T_2$ and $T_3$ respectively are as shown. Their temperatures are such that:

Two stars $A$ and $B$ radiate maximum energy at the wavelengths of $360 \ nm$ and $480 \ nm$ respectively. Then the ratio of the surface temperatures of $A$ and $B$ is

Two metal spheres have radii $r$ and $2r$ and they emit thermal radiation with maximum intensities at wavelengths $\lambda$ and $2\lambda$ respectively. The respective ratio of the radiant energy emitted by them per second will be .........

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