An electron has a total energy of $\text{2 MeV}$. Calculate the effective mass of the electron in $\text{kg}$ and its speed. Assume rest mass of electron $\text{0.511 MeV}$.

The ionization energy of gaseous $\mathrm{Na}$ atoms is $495.5 \mathrm{kJ} {\mathrm{mol}}^{-1}$. The lowest possible frequency of light that ionizes a sodium atom is 

$(\text{h}=\text{6.626}\times 10^{-34} Js, N_{\text{A}}=\text{6.022}\times 10^{23} {mol}^{-1})$

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A: Loss of electron from hydrogen atom results in nucleus of $~1.5\times {10}^{–3} \mathrm{pm}$ size.

Reason R: Proton $\left({\mathrm{H}}^{+}\right)$ always exists in combined form.

In the light of the above statements, choose the most appropriate answer from the options given below:

Electrons in a cathode ray tube have been emitted with a velocity of $1000 {\mathrm{ms}}^{-1}$. The number of following statements which is/are true about the emitted radiation is

Given : $\mathrm{h}=6\times {10}^{-34}\mathrm{Js},{\mathrm{m}}_{\mathrm{e}}=9\times {10}^{-31} \mathrm{kg}$

(A ) The deBroglie wavelength of the electron emitted is $666.67 \mathrm{nm}$

(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..