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 the North Star is

A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

A hot liquid kept in a beaker cools from $80\,^oC$ to $70\,^oC$ in $2\, min$. If the  surrounding temperature is $30\,^oC$, then the time of cooling of the same liquid from  $60\,^oC$ to $50\,^oC$ …….. $\sec$

A beaker full of hot water is kept in a room. If it cools from $80\,^oC$ to $75\,^oC$  in $t_1$ minutes, from $75\,^oC$ to $70\,^oC$ in $t_2$ minutes and from $70\,^oC$  to $65\,^oC$  in $t_3$ minutes then

A body cools from a temperature $60\,^oC$ to $40\,^oC$ in $10$ minutes. The room temperature is $20\,^oC$ . Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next $10$ minutes will be……… $^oC$