Ratio of velocities of electrons of hydrogen atom in $1^{st}$,$2^{nd}$,$3^{rd}$ orbit is

What is the ratio of time periods $(T_1 / T_2)$ in the second orbit of a hydrogen atom to the third orbit of a $He^{+}$ ion?

If the work function of a metal is $6.63 \times 10^{-19} \ J$,the maximum wavelength of the photon required to remove a photoelectron from the metal is $.... \ nm$. (Nearest integer)
[Given : $h = 6.63 \times 10^{-34} \ J \ s$,and $c = 3 \times 10^{8} \ m \ s^{-1}$ ]

According to Bohr's theory,
$E_{n} = \text{Total energy}, K_{n} = \text{Kinetic energy}, V_{n} = \text{Potential energy}, r_{n} = \text{Radius of } n^{\text{th}} \text{ orbit}$
Match the following:

Column $I$	Column $II$
$A$. $V_{n} / K_{n} = ?$	$P$. $0$
$B$. If radius of $n^{\text{th}}$ orbit $\propto E_{n}^{x}, x = ?$	$Q$. $-1$
$C$. Angular momentum in lowest orbital	$R$. $-2$
$D$. $1/r_{n} \propto Z^{y}, y = ?$	$S$. $1$

Which of the following activities can be compared to the concept of quantisation?

The radius of a hydrogen atom in its ground state is $0.53 \ \mathring{A}$. The radius of the $Li^{2+}$ ion in the same state (atomic number = $3$) is ............. $\mathring{A}$.