The difference between the radii of $3^{rd}$ and $4^{th}$ orbits of $Li^{2+}$ is $\Delta R_{1}$. The difference between the radii of $3^{rd}$ and $4^{th}$ orbits of $He^{+}$ is $\Delta R_{2}$. Ratio $\Delta R_{1} : \Delta R_{2}$ is :

Bohr's model cannot explain the emission spectrum of

$A$ bulb emits light of wavelength $4500 \ \mathring{A}$. The bulb is rated at $150 \ W$ and $8 \ \%$ of the energy is emitted as light. What is the number of photons emitted by the bulb in $1 \ s$?

Based on the equation $\Delta E = - 2.0 \times 10^{-18} \, J \left( \frac{1}{n_2^2} - \frac{1}{n_1^2} \right)$,the wavelength of the light that must be absorbed to excite a hydrogen electron from level $n = 1$ to level $n = 2$ will be: $(h = 6.625 \times 10^{-34} \, J \, s, c = 3 \times 10^8 \, m \, s^{-1})$

If the velocity of an electron in the $n^{th}$ orbit of a hydrogen atom is $0.0109 \times 10^{10} \, cm \, s^{-1}$,what is the value of $n$?

Match the spectral lines given in List-$I$ with their corresponding lower energy transitions given in List-$II$.

List-$I$	List-$II$
$(1)$ Lyman	$(A)$ $n = 5 \to n = 4$
$(2)$ Paschen	$(B)$ $n = 3 \to n = 2$
$(3)$ Brackett	$(C)$ $n = 6 \to n = 5$
$(4)$ Balmer	$(D)$ $n = 4 \to n = 3$
	$(E)$ $n = 7 \to n = 6$