When an electron in a hydrogen atom jumps from an infinite state to the first stationary state,the wavelength of the emitted radiation will be ...... (Rydberg constant = $1.097 \times 10^7 \ m^{-1}$):

Calculate the radius of the first orbit of $He^{+}$. (in $pm$)

In Rutherford's experiment,generally the thin foil of heavy atoms,like gold,platinum etc. have been used to be bombarded by the $\alpha$-particles. If the thin foil of light atoms like Aluminium etc. is used,what difference would be observed from the above results?

Match the principles given in List-$I$ with their discoverers given in List-$II$.

List-$I$	List-$II$
$(1)$ Exclusion Principle	$(A)$ Hund
$(2)$ Multiplicity Rule	$(B)$ Heisenberg
$(3)$ Uncertainty Principle	$(C)$ Einstein
$(4)$ Quantum Theory	$(D)$ Planck
	$(E)$ Pauli

When $\alpha$-particles are sent through a thin metal foil,most of them go straight through the foil because

According to Bohr's atomic theory :-
$A$. Kinetic energy of electron is $\propto \frac{Z^{2}}{n^{2}}$.
$B$. The product of velocity $(v)$ of electron and principal quantum number $(n)$,'$vn$' $\propto Z^{2}$.
$C$. Frequency of revolution of electron in an orbit is $\propto \frac{Z^{3}}{n^{3}}$.
$D$. Coulombic force of attraction on the electron is $\propto \frac{Z^{3}}{n^{4}}$.
Choose the most appropriate answer from the options given below :