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

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

The density of neutrons is of the order

Provide general information about the fundamental particles of an atom.

$A$ particle having the same charge and $200$ times greater mass than that of an electron is:

Which of the following statements is correct about the cathode rays?
$1$. These rays start from anode and move towards cathode.
$2$. They are visible with human eye.
$3$. In presence of electric and magnetic fields,they behave like positively charged particles.
$4$. Their characteristic does not depend on the nature of material at electrode.