When an electron jumps from a lower to a higher orbit,its energy

For an emission line of atomic hydrogen from $n_i = 8$ to $n_f = n$,the plot of wave number $(\bar{\nu})$ against $(\frac{1}{n^2})$ will be (The Rydberg constant,$R_H$ is in wave number unit).

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?

In an emission spectrum,the transitions $n_2 \to n_1$,$n_3 \to n_2$,$n_4 \to n_3$,and $n_5 \to n_4$ emit energies $E_1, E_2, E_3$,and $E_4$ respectively. What is the increasing order of these energies?

According to Bohr's theory,the angular momentum of an electron in the $5^{th}$ orbit is ....... (in $h/\pi$)

Which developments played a role in the formation of Bohr's model of the atom?