CBSE
Multiple Choice QuestionsA 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
An electron in hydrogen atom first jumps from third excited state to second excited state and then from second excited to the first excited state. The ratio of the wavelengths λ1:λ2 emitted in the two cases is
7/5
27/20
27/5
27/5
The ratio of escape velocity at earth (Ve) to the escape velocity at a planet (vp) whose radius and mean density are twice as that of earth is,
1:
1:4
1:
1:
Consider 3rd orbit of He+ (Helium), using non-relativistic approach, the speed of electron in this orbit will be (given K= 9 x 109 constant, Z=2 and h (Planck's constant = 6.6 x 10-34 Js-1
2.92 x 106 m/s
1.46 x 106 m/s
0.73 x 106 m/s
0.73 x 106 m/s
A proton carrying 1 MeV kinetic energy is moving in a circular path of radius R in the uniform magnetic field. What should be the energy of an alpha particle to describe a circle of the same radius in the same field.
2 MeV
1 MeV
0.5 MeV
0.5 MeV
The wavelength λe of an electron and λp of a photon of same energy E are related by
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
An electron of a stationary hydrogen atom passes from the fifth energy level to ground level. The velocity that the atom acquired as a result of photon emission will be
Given the value of rydberg constant is 10 m-1, the wave number of the last line of the Balmer series in hydrogen spectrum will be:
0.5 x 107 m-1
0.25 x 107 m-1
2.5 x107 m-1
2.5 x107 m-1
The transition from the state n = 3 to n=1 in a hydrogen-like atom results in ultraviolet radiation. Infrared radiation will be obtained in the transition from.
2→ 1
3 →2
4 → 2
4 → 2
