Magnetic field at the centre of the hydrogen atom due to motion of electron in $$\mathrm{n}^{\text {th }}$$ orbit is proportional to

An excited hydrogen atom emits a photon of wavelength $$\lambda$$ in returning to ground state. The quantum number $$n$$ of the excited state is ($$R=$$ Rydberg's constant)

When an electron is excited from its 4 th orbit to 5 th stationary orbit, the change in the angular momentum of electron is approximately.

(Planck's constant $$=h=6.63 \times 10^{-34} \mathrm{~J}-\mathrm{s}$$ )

A radioactive sample has half-life of 5 years. The percentage of fraction decayed in 10 years will be