The force acting on the electrons in hydrogen atom (Bohr's theory) is related to the principle quantum number $$n$$ as

If the speed of an electron of hydrogen atom in the ground state is $2.2 \times 10^6 \mathrm{~m} / \mathrm{s}$, then its speed in the third excited state will be

In hydrogen emission spectrum, for any series, the principal quantum number is $n$. Corresponding maximum wavelength $\lambda$ is ( $R=$ Rydberg's constant)

When the electron in hydrogen atom jumps from fourth Bohr orbit to second Bohr orbit, one gets the