Hydrogen atom in ground state is excited by a monochromatic radiation of . The number of spectral lines in the resulting spectrum emitted will be,

• 3

• 2

• 6

• 6

The wavelength λ_e of an electron and λ_p of a photon of same energy E are related by

A certain mass of hydrogen is changed to helium the process of fusion. The mass defect in fusion reaction is 0.02866 u. The energy liberated per u is (given 1 u =931 MeV)

• 2.67 MeV

• 26.7 MeV

• 6.675 MeV

• 6.675 MeV

Ratio of longest wavelength corresponding to Lyman and Balmer series in hydrogen spectrum is 

• 5/27

• 3/23

• 7/29

• 7/29

Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the voltage is increased to 100 kV then the de - Broglie wavelength associated with the electrons would

• decrease by 2 times

• decrease by 4 times

• increase by 4 times

• increase by 4 times

The wavelength of the first line of Layman series for the hydrogen atom is equal to that of the second line of Balmer series for a hydrogen-like an ion. The atomic number Z  of hydrogen-like ion is 

• 4

• 1

• 2

• 2

In the spectrum of hydrogen, the ratio of the longest wavelength in the Lyman series to the longest wavelength in the Balmer series is 

• 4/9

• 9/4

• 27/5

• 27/5

108.

The energy of a hydrogen atom in the ground state is -13.6 eV. The energy of a He⁺ ion in the first excited state will be

• -13.6 eV

• -27.2 eV

• -54.4eV

• -54.4eV

The potential difference that must be applied to stop the fastest photoelectrons emitted by a nickel surface, having work function 5.01 eV, when ultraviolet light of 200 nm falls on it, must be

• 2.4 V

• -1.2 V

• -2.4 V

• -2.4 V

The electron in the hydrogen atom jumps from excited state (n=3) to its ground state (n=1) and the photons thus emitted irradiate a photosensitive material. If the work functions of the material is 5.1 eV, the stopping potential is estimated to be (the energy of the electron is nth state E_n = -13.6/n² eV)

• 5.1 V

• 12.1 V

• 17.2 V

• 17.2 V