If a black wire of platinum is heated, its colour first appears red, then yellow, and finally white. This can be understood on the basis of:

Experimental investigations show that the intensity of solar radiation is maximum for a wavelength $480 \, nm$ in the visible region. Estimate the surface temperature of the sun. Given Wien's constant $b = 2.88 \times 10^{-3} \, mK$.

The intensity of radiation emitted by the sun has its maximum value at a wavelength of $510\;nm$ and that emitted by the north star has the maximum value at $350\;nm$. If these stars behave like black bodies,then the ratio of the surface temperature of the sun and north star is

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

On observing light from three different stars $P, Q$ and $R$, it was found that the intensity of violet colour is maximum in the spectrum of $P$, the intensity of green colour is maximum in the spectrum of $R$, and the intensity of red colour is maximum in the spectrum of $Q$. If $T_P, T_Q$ and $T_R$ are the respective absolute temperatures of $P, Q$ and $R$, then it can be concluded from the above observations that:

The radiation energy density per unit wavelength at a temperature $T$ has a maximum at a wavelength $\lambda_0$. At temperature $2T$,it will have a maximum at a wavelength: