Rutherford's scattering experiment is related to the size of the

When beryllium is bombarded with $\alpha$-particles,extremely penetrating radiations which cannot be deflected by electrical or magnetic field are given out. These are

Arrange the following particles in the increasing order of their $e/m$ ratio: electron $(e)$,proton $(p)$,neutron $(n)$,and $\alpha$-particle $(\alpha)$.

The increasing order for the values of $e/m$ $(\text{charge/mass})$ is :

Electrons in a cathode ray tube have been emitted with a velocity of $1000 \, m \, s^{-1}$. The number of following statements which is/are true about the emitted radiation is
Given : $h = 6 \times 10^{-34} \, Js$,$m_{e} = 9 \times 10^{-31} \, kg$.
$(A)$ The de Broglie wavelength of the electron emitted is $666.67 \, nm$.
$(B)$ The characteristic of electrons emitted depend upon the material of the electrodes of the cathode ray tube.
$(C)$ The cathode rays start from cathode and move towards anode.
$(D)$ The nature of the emitted electrons depends on the nature of the gas present in cathode ray tube.

The $\alpha$-particle is identical with