Arrange the $\frac{e}{m}$ (charge-to-mass) ratio in increasing order for the following particles: $e, p, n, \alpha$.

The nucleus of an atom can be assumed to be spherical. The radius of the nucleus of mass number $A$ is given by $1.25 \times 10^{-13} \times A^{1/3} \ cm$. The radius of the atom is $1 \ \mathring{A}$. If the mass number is $64$,then the fraction of the atomic volume that is occupied by the nucleus is:

Positive charge in an atom is:

Which of the following will not show deflection from the path on passing through an electric field?

Among the following,the correct statement about the cathode ray discharge tube is:

Positronium is the name given to an atom-like combination formed between