What will be the angular width of the central maxima in Fraunhofer diffraction when light of wavelength $6000 \, \mathring{A}$ is used and the slit width is $12 \times 10^{-5} \, cm$? (in $rad$)

$A$ space $2.5 \ cm$ wide between two large plane surfaces is filled with oil. The force required to drag a very thin plate of area $0.5 \ m^2$ just midway between the surfaces at a speed of $0.5 \ m/s$ is $1 \ N$. The coefficient of viscosity in $kg/(m \cdot s)$ is:

$A$ circular disc of radius $R$ is removed from a bigger circular disc of radius $2R$ such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance $\alpha R$ from the centre of the bigger disc. The value of $\alpha$ is

If $|x| < \frac{1}{2}$,then the coefficient of $x^r$ in the expansion of $\frac{1+2x}{(1-2x)^2}$ is

The oxide of nitrogen formed by thermal decomposition of $NH_4NO_3$ is

Which property of hydrogen distinguishes it from alkali metals?