In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is

A proton is fired from very far away towards a nucleus with charge $Q=120 \ e$, where $e$ is the electronic charge. It makes a closest approach of $10 \ fm$ to the nucleus. The de Brogle wavelength (in units of $fm$ ) of the proton at its start is :

(take the proton mass, $m _0=(5 / 3) \times 10^{-27} kg , h / e =4.2 \times 10^{-15} J / s / C ; \frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 m / F ; 1 fm =10^{-15} m$ ) 

Describe Geiger-Marsden scattering experiment. 

The ratio of speed of an electron in ground state in Bohrs first orbit of hydrogen atom to velocity of light in air is

An $\alpha$- particle of $5\ MeV$ energy strikes with a nucleus of uranium at stationary at an scattering angle of $180^o$. The nearest distance upto which $\alpha$- particle reaches the nucleus will be of the order of

Assertion $(A)$ : The magnetic moment $(\mu)$ of an electron revolving around the nucleus decreases with increasing principle quantum number $(n)$.

Reason $(R)$ : Magnetic moment of the revolving electron, $\mu \propto n$.