ATOMIC PHYSICS

1. A narrow electron beam passes undeviated through an electric field E = 3x10^4 V/m and overlapping magnetic field B = 2x 10^-3 Wb/m2. The electron motion, electric field and magnetic field are mutually perpendicular. The speed of the electron is

60 ms^-1

10.3x10^7 ms^-1

1.5x 10^7 ms^-1

0.67x10^-7 ms^-1

2. He-Ne laser system consists of a quartz discharge tube containing helium and neon in the ratio of

1:1

1:2

2:1

1:4

3. The pressure in the discharge tube at which Crooke's dark space fills the whole tube is

10 mm of Hg

1mm of Hg

0.1 mm of Hg

0.01 mm of Hg

4. The chromium ions in the ruby rod

Absorb red light

Absorb green light

Absorb blue light

Emit green light

5. After pumping process is laser

The number of atoms in the ground state is greater than the number of atoms in the excited state

The number of atoms in the excited state is greater than the number of atoms in the ground state

The number of atoms in the ground state is equal to the number atoms in the excited state.

O atoms are available in the excited state.

6. In hydrogen atom, which of the following transitions produce a spectral line of maximum frequency

2---->1

6---->2

4---->3

5---->2

7. In hydrogen atom, which of the following transitions produce a spectral line of maximum wavelength

2---->1

4---->1

6---->5

5---->2

8. The energy of a photon of characteristic X-ray from a Coolidge tube comes from

The kinetic energy of the free electrons of the target

The kinetic energy of ions of the target

The kinetic energy of the striking electron

An atomic transition in the target

9. X-ray is

Phenomenon of conversion of kinetic energy into radiation

Conversion of momentum

Conversion of energy into mass

Principle of conservation of charge

10. The elliptical orbits of electron in the atom were proposed by C

J.J. Thompson

Bohr

Sommerfield

De Broglie

11. Energy levels A,B,C of a certain atom correspond to increasing values of energy (i.e) E(A)<E(B)<E(C). If Y1,Y2,Y3 are the wavelengths of radiations corresponding to the transitions Cto B, B to A and C to A resply. Which of the following statements is correct B

Y3 =Y1+Y2

Y3 = (Y1Y2)/Y1+Y2

Y1 = Y2+Y3=0

Y2^3 = Y1^2+ Y2^2

12. According to Rutherford atom model, the spectral lines emitted by an atom is

Line spectrum

Continuous spectrum

Continuous absorption spectrum

Band spectrum

13. The first excitation potential energy or the minimum energy required to excite the atom from ground state of hydrogen atom is

13.6eV

10.2eV

3.4eV

1.89eV

14. The ratio of the radii of the first three Bohr orbits is

1:1/2:1/3

1:2:3

1:4:9

1:8:27

15. .According to Bohr's postulates, which of the following quantities take discrete values

Kinetic energy

Potential energy

Angular momentum

Momentum

16. In an X-ray tube, the intensity of the emitted X-ray beam is increased by increasing the filament current

Increasing the filament current

Decreasing the filament current

Increasing the target potential

Decreasing the target potential

17. A Coolidge tube operates at 24800V. The maximum frequency of x- radiation emmitted from Coolidge tube is

6 x 10^18 Hz

3x10^18Hz

6x10^8Hz

3x10^8Hz

18. The shortest wavelength of Balkmer series is R/4 C

R/4

5R/36

4

36/5R

19. The cathode rays are

A stream of electrons

A stream of positive ions

A stream of uncharged particles

The same as canal rays

20. The minimum potential required to excite a free neutral atom from its ground state to higher state is defined as critical potential

Excitation potential

Critical potential

Ionization potential

Stopping potential

Atomic Physics