An $X$-ray tube is operated at $50 \ kV$. The minimum wavelength produced is ..... $\mathring{A}$.

$A$ wire of length $10 \, cm$ translates in a direction making an angle of $60^\circ$ with its length. The plane of motion is perpendicular to a uniform magnetic field of $1.0 \, T$ that exists in the space. Find the $emf$ induced between the ends of the rod if the speed of translation is $20 \, cm/s.$

Two nuclei have their mass numbers in the ratio of $1:3$. The ratio of their densities would be

On combustion of $Li$,$Na$,and $K$ in excess of air,the major oxides formed,respectively,are:

If $5 \cos x + 12 \cos y = 13$,then the maximum value of $5 \sin x + 12 \sin y$ is:

Which of the following plants are used as green manure in crop fields and sandy soils?