The ratio of the radius of the second orbit of $Li^{2+}$ to that of the third orbit of $Be^{3+}$ is:

According to the Bohr theory,which of the following transitions in the hydrogen atom will give rise to the least energetic photon?

State whether the following statements are true or false:
$(i)$ In Rutherford's atomic model,the Coulombic forces between the nucleus and electrons are mathematically similar to the gravitational forces $F = G \frac{m_1 m_2}{r^2}$.
$(ii)$ Out of every $20000$ $\alpha$-particles,$\sim 10$ particles bounce back after hitting the gold foil.
$(iii)$ In Rutherford's experiment,a zinc sulfide $(ZnS)$ fluorescent screen is placed around the gold foil.
$(iv)$ Rutherford's $\alpha$-particle scattering experiment is related to the size of the atomic nucleus.

When light is directed at the metal surface,the emitted electrons

Find the energy of a photon having a wavelength of $6000 \ \mathring{A}$. (Given: $h = 6.62 \times 10^{-27} \ erg \cdot s$)

Which of the following statements regarding the $H$ atom spectrum is correct?