11) The ratio of radii of Bohr′s 3^rd and 4^th orbits in H atom are:

12) Ionisation energy of Na atom is 4.946 x 10² kJ⁄mol. The wavelength of radiation sufficient to ionise Na atom is:

13) If the shortest wavelength of H atom in Lyman series is x, then the longest wavelength in Paschen series of He⁺ is:

14) A 0.66 kg ball is moving with a speed of 100 m⁄s. The associated wavelength will be:

15) If the shortest wavelength of H atom in Lyman series is a, then the longest wavelength in Balmer series of He⁺ is: