**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. P.fund 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 follo****wing 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__