Modern Physics II

1. Laser can be made by creating:

a. Assembly

b. Population inversion

c. Metastable state

d. All of the above

Correct Option: d


2. The speed of an electron in the orbit of hydrogen atom in the ground state is:

a. c/2

b. c/137

c. c/10

d. c

Correct Option: b


3. What is the speed of electron in the first Bohr orbit?

a. 3 * 10(8) m/s

b. 2.19 * 10(6) m/s

c. 1.6 * 10(6) m/s

d. 2.2 * 10(-6) m/s

Correct Option: b


4. The spectral lines of Paschen series (visible region) are produced when electron jumps from higher orbit to

a. 1st orbit

b. 3rd orbit

c. 4rth orbit

d. 2nd orbit

Correct Option: b


5. Which orbital has dumb–bell shape

a. s-orbital

b. p-orbital

c. f-orbital

d. d-orbital

Correct Option: b


6. The regions of spectrum are

a. 8

b. 3

c. 7

d. 5

Correct Option: c


7. . If a photon is reflected from the mirror then the change in momentum of each photon is_______________?

a. Double

b. zero

c. half

d. one

Correct Option: a


8. A spinning electron creates

a. magnetic field

b. electric field

c. quantum field

d. none

Correct Option: a


9. According to Bohr when electron jumps from any higher orbit to third orbit, the spectral lines so emitted are called:

a. Paschen series

b. Balmer series

c. Lyman series

d. series

Correct Option: a


10. According to Bohr’s postulates which of the following quantities takes discrete values?

a. Angular momentum

b. Kinetic energy

c. Momentum

d. Potential energy

Correct Option: a


11. According to Bohr’s theory of the hydrogen atom. Only those orbits around the nucleus are allowed along with angular momentum of electron is:

a. n(2π/h)

b. n/2πh

c. nh/2π

d. 2π/nh

Correct Option: c


12. All atoms are principally composed of few fundamental particles which are in number

a. 4

b. 5

c. 3

d. 2

Correct Option: c


13. Alpha particles are identical to

a. hydrogen atoms

b. helium atoms

c. fast moving electrons

d. helium nuclei

Correct Option: d


14. Bohar theory was modified by

a. sumerfield

b. planks

c. rutherford

d. hund

Correct Option: b


15. electrons in an atom held in atom due to

a. coloumb interaction

b. nuclear force

c. atomic force

d. none

Correct Option: a


16. Helium-Neon laser discharge tube contains neon:

a. 0.82

b. 0.89

c. 0.15

d. 0.25

Correct Option: c


17. If n number of the photon is striking on a metal surface then total momentum exerted is

a. p

b. n

c. 0

d. none

Correct Option: a


18. If the electron in the hydrogen atoms is excited to n = 5 state, the number of  frequencies present in the radiation emitted is :

a. 5

b. 8

c. 10

d. 4

Correct Option: c


19. If the radius of first orbit of hydrogen atom is 0.53Å, the radius of second orbit will be:

a. 0.2120 Å

b. 21.200 Å

c. 0.142 Å

d. 2.120 Å

Correct Option: c


20. In He-Ne laser, the laser action is produced by:

a. Electrons Ne

b. He-Ne both

c. Ne only

d. Electrons of He

Correct Option: c


21. In Stimulated Absorption, what is the lifetime of atoms ground state?

a. 1 s

b. 1 min

c. Infinity

d. 1 hour

Correct Option: c


22. in which of following year laser is discovered

a. 1916

b. 1995

c. 1960

d. 1840

Correct Option: c


23. Life time of excited states is:

a. 10-8 s

b. 10-3sec

c. 10-5 s

d. none

Correct Option: a


24. Orbitals having same energy are called

a. hybrid orbitals

b. valence orbitals

c. d–orbitals

d. degenerate orbitals

Correct Option: d


25. Quantum number values for 3p orbitals are

a. n = 0,  l = 3

b. n = 2,  l = 1

c. n = 1,  l = 3

d. n = 3,  l = 1

Correct Option: d


26. Splitting of spectral lines under the influence of a electric field is called

a. compton effect

b. Stark effect

c. Zeeman effect

d. Photoelectric effect

Correct Option: b


27. The angular momentum of an electron in a hydrogen atom is proportional to:

a. √r

b. 1/√r

c. 1/r

d. r(2)

Correct Option: a


28. The energy of bounded electron in H atom is

a. negative

b. positive

c. zero

d. none of these

Correct Option: a


29. The ionisation potential of a hydrogen atom is 13.6 volt. The energy required to remove an electron from the second orbit of hydrogen is:

a. 27.2 eV

b. 3.4 eV

c. 13.6 eV

d. 6.8 eV

Correct Option: b


30. The ionization energy of hydrogen is:

a. zero

b. 13.6 eV

c. 49.8eV

d. 3.4 eV

Correct Option: b


31. The linear momentum of a photon is

a. Hv/c

b. c2/hv

c. Hv/c2

d. Zero

Correct Option: d


32. The radius of electron’s second stationary orbit in Bohr’s atom is R. The radius of the third orbit will be:

a. 2.25

b. 3 R

c. 9 R

d. R/3

Correct Option: a


33. The radius of first orbit of hydrogen atom

a. 0.429 Ao

b. 0.229 Ao

c. 0.529 Ao

d. 0.329 Ao

Correct Option: c


34. The radius of the first Bohr orbit is ao. The nth orbit has a radius:

a. ao/n2

b. nao

c. ao/n

d. n2ao

Correct Option: b


35. The ratio of magnetic dipole moment of an electron of charge e and mass m in the Bohr orbit in hydrogen to the angular momentum of the electron in the orbit is:

a. 2m/e

b. e/2m

c. m/e

d. e/m

Correct Option: b


36. The rest mass of a photon is

a. Very small

b. 1.67 x 10-27 kg

c. Zero

d. Infinite

Correct Option: c


37. The value of Planck’s constant “h” is

a. 3.1 x 10–4 J sec

b. 6.625 x 10–34 JS

c. 6.625 x 10–23 kJ

d. 9.8 x 10–12 k cal

Correct Option: b


38. the velocity of an electron in most inner orbit is

a. zero

b. highest

c. mean

d. lowest

Correct Option: b


39. The volume of space in which there is 95% chance of finding an electron is

a. orbit

b. degenerate orbital

c. atomic orbital

d. quantized orbital

Correct Option: a


40. The wavelength range of visible spectrum is

a. 300–400 nm

b. 400–750 nm

c. 350–600 nm

d. 200–400 nm

Correct Option: b


41. To find longest wavelength radiation in Balmer series the value of ‘n’ used is:

a. 2

b. ∞

c. 4

d. 3

Correct Option: c


42. What is the speed of electron in the first Bohr orbit?

a. 2.2 * 10-6 m/s

b. 2.19 * 106 m/s

c. 1.6 * 106 m/s

d. 3 * 108 m/s

Correct Option: b


43. when hydrogen atom is in its first excited level then its radious is

a. twice

b. same

c. half

d. four time its ground state radius

Correct Option: d


44. when hydrogen atom is raised from ground state to excited state then

a. P.E increase & K.E decrease

b. P.E decrease & K.E increase

c. both decrease

d. remais same

Correct Option: a


45. Which color of light has the longest wavelength ?

a. yellow

b. red

c. blue

d. green

Correct Option: b


46. which of following transition between rotational energy level is not possible

a. J=2 to J=1

b. J=0 to J=1

c. J=1 to J=0

d. J=3 to J=1

Correct Option: d


47. Which of the following electromagnetic waves have the smallest wavelength?

a. X-rays

b. γ-rays

c. UV-rays

d. Infrared rays

Correct Option: b


48. Which of the following is not a characteristic of LASERS?

a. Coherent

b. Monochromatic

c. Intense

d. Divergent

Correct Option: d


49. Which of the following quantum numbers describes shape of an electron in an atom

a. principal quantum

b. spin quantum

c. magnetic quantum

d. azimuthal quantum

Correct Option: d


50. X-rays were discovered by:

a. Becquerel

b. Van Lave

c. Marie Curie

d. Roentgen

Correct Option: d