Radius of the nucleus is equal to $10^{-12} \ cm$ and that of the atom is equal to $10^{-8} \ cm$. What is the fraction of the volume of the atom occupied by the nucleus?

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:

The space between the proton and the electron in a hydrogen atom is $......$.

The mass of a neutron is nearly

The $\alpha$-particle is identical with

Fill in the blanks given below:
$(i)$ The picture on the television screen is visible due to the presence of .......... on the screen.
$(ii)$ In the presence of electric and magnetic fields,cathode rays are known as .......... .
$(iii)$ The measurement of the $e/m_e$ ratio for electrons was performed by the scientist .......... .
$(iv)$ In a cathode ray tube,the greater the magnitude of the charge on the particles,the .......... the deflection of the particles.