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

The radius of the second excited state of $Li^{2+}$ is ................ $\mathring{A}$.

If the radius of the first orbit of a hydrogen-like ion is $1.763 \times 10^{-2} \ nm$,the energy associated with that orbit (in $J$) is

$A$ $150 \ W$ bulb emits light of wavelength $6600 \ \mathring{A}$ and only $8 \%$ of the energy is emitted as light. How many light photons are emitted by the bulb per second?

$(i)$ The energy associated with the first orbit in the hydrogen atom is $-2.18 \times 10^{-18} \, J \, atom^{-1}$. What is the energy associated with the fifth orbit?
$(ii)$ Calculate the radius of Bohr's fifth orbit for the hydrogen atom.

If the wavelength of an electromagnetic radiation is $2000 \ \text{Å}$,what is its energy in ergs?