The neutrino has:

Fill in the blanks:
$(i)$ For the discovery of neutrons,$\alpha$-particles were bombarded on a thin sheet of ......... .
$(ii)$ For the $\alpha$-particle scattering experiment,Rutherford used a gold foil of thickness ......... .
$(iii)$ The radius of an atom is approximately ......... and the radius of the nucleus is ......... .
$(iv)$ The entire positive charge of an atom is concentrated in a very small region,which is called ......... .

Neutrons are obtained by

Write down the results of the cathode ray discharge tube experiment.

Which one of the following pairs is not correctly matched?

The mass of the proton is $1840$ times that of an electron. If a proton is accelerated through a potential difference of $1 \,kV$,the kinetic energy of the proton would be