From the statements given below:$(A)$ The angular momentum of an electron in $n^{\text {th }}$ orbit is an integral multiple of $h$.$(B)$ Nuclear forces do not obey inverse square law.$(C)$ Nuclear forces are spin dependent.$(D)$ Nuclear forces are central and charge independent.$(E)$ Stability of nucleus is inversely proportional to the value of packing fraction.

Choose the correct answer from the options given below :

A nucleus represented by the symbol ${ }_{Z}^{ A } X$ has

Consider the following statements ( $X$ and $Y$ stand for two different elements):

$(I)$ ${ }_{32}^{65} X$ and ${ }_{33}^{65} Y$ are isotopes.

$(II)$ ${ }_{42}^{86} X$ and ${ }_{42}^{85} Y$ are isotopes.

$(III)$ ${ }_{85}^{174} X$ and ${ }_{88}^{177} Y$ have the same number of neutrons.

$(IV)$ ${ }_{92}^{235} X$ and ${ }_{94}^{235} Y$ are isobars.

Which of the above statements are correct?

$\pi $ mesons can be

The radius of germanium $(Ge)$ nuclide is measured to be twice the radius of ${}_4^9Be$ . The number of nucleons in $Ge$ are

The charge density in a nucleus varies with distance from the centre of the nucleus according to the curve in Fig.