The difference between the radii of 3^rd and 4^th
orbits of Li²⁺ is R₁ . The difference between the
radii of 3^rd and 4^th orbits of He⁺ is $$\Delta $$R₂ .
Ratio $$\Delta $$R₁ : $$\Delta $$R₂ is :

The shortest wavelength of H atom in the Lyman series is $$\lambda $$₁. The longest wavelength in the Balmar series of He⁺ is :

The region in the electromagnetic spectrum where the Balmar series lines appear is :

Consider the hypothetical situation where the azimuthal quantum number, $$l$$, takes values 0, 1, 2, ....., n + 1, where n is the principal quantum number. Then, the element with atomic number :