In the hydrogen spectrum,if an electron transitions from the $6^{th}$ orbit to the $3^{rd}$ orbit,what is the total number of spectral lines in the visible region?

The ionization energy of a singly ionized helium ion $(He^+)$ is equal to:

The energy of a photon is calculated by ......

The kinetic energy of an electron in the second Bohr orbit of a hydrogen atom is equal to $\frac{h^{2}}{xma_{0}^{2}}$. The value of $10x$ is ........ . ($a_{0}$ is radius of Bohr's orbit) (Nearest integer) [Given : $\pi=3.14$]

Which of the following is the energy of a possible excited state of hydrogen? $........... \ eV$

The energy of an electron in the $n^{th}$ orbit of a hydrogen atom is given by: