When an electron transitions from the $n^{th}$ orbit to the $2^{nd}$ orbit in a $Li^{2+}$ ion,$15$ spectral lines are obtained. What is the value of $n$?

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

The energy of the second orbit of a hydrogen atom is $-5.45 \times 10^{-19} \ J$. What is the energy of the first orbit of $Li^{2+}$ ion (in $J$)?

When an electron drops from a higher energy level to a lower energy level,then

The energy of an electron in the second Bohr orbit of a hydrogen atom is:

The wavelength corresponding to an electronic transition between two orbits of a hydrogen atom is $912 \mathring{A}$. The wavelength (in $\mathring{A}$) for the same electronic transition in $Li^{2+}$ is