Which of the following species has the same radius as that of the hydrogen atom in the $n = 1$ state?

The wavelength of the first line of the Balmer series is $656 \ nm$. Calculate the wavelength of the second line of this series. (Note: First line means $n=3 \to n=2$ and second line means $n=4 \to n=2$)

Assertion $:-$ Emitted radiation will fall in the visible region when an electron jumps from $n=4$ to $n=2$ in a hydrogen atom.
Reason $:-$ The frequency of radiation of the Lyman series belongs to the visible region for a hydrogen atom.

If the radius of the $3^{\text{rd}}$ Bohr's orbit of hydrogen atom is $r_{3}$ and the radius of $4^{\text{th}}$ Bohr's orbit is $r_{4}$,then which of the following relations is correct?

Energy and radius of the first Bohr orbit of $He^{+}$ and $Li^{2+}$ are: $[$Given $R_{H} = 2.18 \times 10^{-18} \ J, a_{0} = 52.9 \ pm$ $]$

Calculate the energy and frequency of the radiation emitted when an electron jumps from $n = 3$ to $n = 2$ in a hydrogen atom.