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

If $A$ is the areal velocity of a planet of mass $M$,its angular momentum is

At the same temperature and pressure,which of the following gases will have the highest kinetic energy per mole?

Which of the following animals possesses a four-chambered heart?

$A$ poster is to be printed on a rectangular sheet of paper of area $18 \ m^2$. The margins at the top and bottom of $75 \ cm$ each and at the sides $50 \ cm$ each are to be left. Then the dimensions i.e. height and breadth of the sheet so that the space available for printing is maximum,are . . . . . . respectively.

If an electric heater is rated at $1000\, W$,then the time required to heat one litre of water from $20\, ^oC$ to $60\, ^oC$ is