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

An $X-$ ray tube is operated at $50\, kV$. the minimum wavelength produced is.......$\mathop A\limits^o $

The ratio between total acceleration of the electron in singly ionized helium atom and hydrogen atom (both in ground state) is

State the dimension of the nucleus from Rutherford experiment. 

For a certain hypothetical one electron atom the wavelength (in $Å$ ) for the spectral lines for transition from $n = p$ to $n = 1$ are given by $\lambda  = \frac{{1500{p^2}}}{{{p^2} - 1}}$ (where $p > 1$ ), then the ionization potential of this element must be ......$V$ (Take $hc = 12420\ eV-Å$ )

The wavelengths of ${K_\alpha }$ $X-$ rays of two metals $'A'$ and $'B'$ $\frac{4}{{1875R}}$ and $\frac{1}{{675R}}$ respectively, where $'R'$ is Rydberg's constant. The number of elements lying between $'A'$ and $'B'$ according to their atomic numbers is