How many spectral lines are obtained when an electron in a hydrogen atom undergoes a transition from the $7^{th}$ Bohr orbit to the $2^{nd}$ orbit?

For a hydrogen $(H)$ atom,what will be the wavelength (in $nm$) associated with the transition of an electron from the infinite energy level to the first energy level? (Rydberg constant = $1.097 \times 10^{7} \ m^{-1}$)

For the $H$ atom,which of the following is the correct order of energy?

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

Bohr’s atomic theory gave the idea of :

What is the experimental evidence in support of the idea that electronic energies in an atom are quantized?