In an atom, two electrons move around the nucleus in circular orbits of radii $R$ and $4R.$ The ratio of the time taken by them to complete one revolution is : (neglect electric interaction)

In the Rutherford's nuclear model of the atom, the nucleus (radius about $10^{-15} \;m$ ) is analogous to the sun about which the electron move in orbit (radius $\approx 10^{-10} \;m$ ) like the earth orbits around the sun. If the dimensions of the solar system had the same proportions as those of the atom, would the earth be closer to or farther away from the sun than actually it is? The radius of earth's orbit is about $1.5 \times 10^{11} \;m.$ The radius of sun is taken as $7 \times 10^{8}\;m$

In an alpha particle scattering experiment distance of closest approach for the $\alpha$ particle is $4.5 \times 10^{-14} \mathrm{~m}$. If target nucleus has atomic number $80$ , then maximum velocity of $\alpha$-particle is . . . . .. $\times 10^5$ $\mathrm{m} / \mathrm{s}$ approximately.

$\left(\frac{1}{4 \pi \epsilon_0}=9 \times 10^9 \mathrm{SI}\right.$ unit, mass of $\alpha$ particle $=$ $\left.6.72 \times 10^{-27} \mathrm{~kg}\right)$

Ionization potential of hydrogen atom is $13.6 V$. Hydrogen atoms in the ground state are excited by monochromatic radiation of photon energy $12.1 eV.$ The spectral lines emitted by hydrogen atoms according to Bohr's theory will be

State the limitations of plum pudding model of the atom. 

Match List $- I$ (Experiment performed) with List $-II$ (Phenomena discovered/associated) and select the correct option from the options given the lists