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MCQ ON LASER: 1.

Which is the property of Laser light

a)

Coherent

b)

Non-coherent

c)

multidirectional

d)

polychromatic

2.

Which is the basis of lasing action

a)

stimulated emission

b)

interference

c)

None

d) all of these

3.

Ordinary light emits

a)

Coherent light

b)

Incoherent light

c)

Stimulated light

d)

Uni- directional Ans :> B

4.

Laser source is highly

a)

Monochromatic

b)

Polychromatic

c)

All of above

d)

Unpolarised Ans :> A

5.

In the absorption process the photon is

a)

absorbed

b)

produced

c)

None

d)

all of these

Ans :> A 6.

In spontaneous emission process the photon is

a)

absorbed

b)

produced

c)

None

d)

all of these Ans :> B

7.

In stimulated emission process the number of coherent photons produced are

a)

2

b)

1

c)

3

d)

4 Ans :> A

8.

The concept of stimulated emission was first put forward by

a)

Maxwell

b)

Newton

c)

Oppenheim

d)

Einstein Ans :> d

9.

The life time of metastable state is

a)

less

b)

more

c)

Equal

d)

zero Ans :> B

10. Which is the property of laser light a)

coherent

b)

monochromaticity

c)

highly directional

d)

all of these Ans :> d

11. The population inversion process is observed due to the existence of

a)

Metastable state

b)

Excited state

c)

Ground state

d)

no state Ans :> A

12. In lasing action, the light amplification is done due to a)

Stimulated emission

b)

Spontaneous emission

c)

Absorption

d) none of these Ans :> A 13. In lasing action, spontaneous emission does not depend on a)

The number of atoms present in the ground state

b)

The intensity of incident light

c)

none of these

d)

all of these Ans :> B

14. Stimulated emission depends on a)

The number of atoms present in the excited state

b)

The intensity of incident light

c)

Both a & b

d) none of these Ans :> C 15. In thermal equilibrium during lasing action, the upward and downward transitions in between ground state and excited is a)

Equal

b)

Not equal

c)

None

d) all of these Ans :> A 16. The probability of spontaneous emission in comparison to stimulated emission is propotiontial to the

a)

Third power of frequency of incident radiation

b)

Fourth power of frequency of incident radiation

c)

None

d)

all of these Ans :> A

17. The Einstein coefficients of stimulated emission and that of absorption numerically a)

Equal

b)

Unequal

c)

None

d)

more Ans :> A

18. Ans :> A In Nd-YAG laser the active medium is a)

Solid

b)

Liquid

c)

Gas

d)

none of these

19. In He-Ne laser, the ratio of Ne-He is a)

1: 10

b)

10: 1

c)

17: 5

d)

20:3 Ans :> A

20. In He-Ne laser, the active medium is a)

solid

b)

liquid

c)

gas

d)

none of these Ans :> c 21. In He-Ne laser, pumping is done by

a)

Optical pumping

b)

Inelastic atom-atom collision

c)

Chemical reactions

d) electric discharge Ans :> d 22. The population inversion in preparing laser beam can be achieved a)

When one of the excited states in more populated that the ground state

b)

When one of the excited state is less population then the ground state

c)

when the population of both the states are equal

d)

none of these Ans :> A 23. In He-gas laser, the ratio of mixture of He gases and Ne gases is

a)

1:10

b)

10:1

c)

11:10

d)

4:7 Ans :> A

24. In He-Ne laser, He has a)

3 energy states

b)

2 energy states

c)

5 energy states

d)

6 energy states

Ans :> A 25. What is the basis of holography a)

recording of hologram

b)

reconstruction of image

c)

both of these

d)

none of these Ans :> c

26. which is the application of laser a)

welding

b)

holography

c)

drilling

d)

all of these Ans :> d

27.Holography is which type of process a) 2D b) 3D c) 4D d) 5D ans: b 28. The reconstruction process in holography involves a) Interference phenomenon b) Diffraction phenomenon c) Both (a) & (b) d) None of these

29. Wavelength of He: Ne laser is a.) 6928 angstrom b) 6428 angstrom c) 6328 angstrom d) 6398 angstrom

30. Resonant cavity in semiconductor-lasers consists of (a) Intrinsic region (b) Junction (c) Two ends of junction (d) Polished ends of junction 31

Pumping source preferred for gaseous lasers is (a) optical pumping (b) electrical pumping (c) chemical pumping (d) X-Ray pumping 32. The laser frequency when the light has the wavelength 800 nm is

a) 375 x 1012 Hz b) 475 x 1015 Hz c) 375 x 109 Hz d) 375 x 1018 Hz 33. What is MASER? a) Microwave amplification by stimulated emission of radiation

34.Pumping system in Nd-YAG is a) 3 level b) 2-level c) 4-level d) Non of above

34. In Nd-YAG what is full form of YAG ? a) Yimmium Aluminium Garnet b) Yttrium Aluminium Gallium c) Yttrium Aluminium Garnet d) Yttrium Argon Garnet

35. Holography is the production of holograms by the use of a)Ordinary light b) white light c) flash lamp d) laser.

MCQ ON OPTICAL FIBER: 1) Acceptance angle is defined as the _______ angle of incidence at the end face of an optical fibre, for which the ray can be propagated in the optical fibre is 1. maximum 2. minimum

3. Either a or b 4. none of the above

2) The core diameter of single mode step index fibre is about: ( ) 1. 2. 3. 4.

60 to 70 µm 8 to 10 µm 100 to 250 µm 50 to 200 µm

3) In multimode graded index fibre, light rays travel _______ in different parts of the fibre. ( ) 1. 2. 3. 4.

at different speeds with same speed both a and b none of the above

4) Step index fiber sustains only a. single mode of propagation b. multimode of propagation c. both (a)&(b) d. none of these

5) Acceptance angle is the a. Minimum angle of incidence

b. Maximum angle of incidence

c. It can be maximum or minimum depending on nature of material used in core

6) In the structure of fibre optic cable, the refractive index of core is always _______the refractive index of cladding. a. Less than b. Equal to c. Greater than d. None of the above

Ans:> c. Greater than

7) In the structure of a fiber, which component provides additional strength and prevents the fiber from any damage? a. Core b. Cladding c. Buffer Coating d. None of the above Ans:> c.Buffer Coating 8) In the structure of fiber, the light is guided through the core due to total internal ______ a. reflection b. refraction c. diffraction d. dispersion ans :> a. reflection

9) Light is confined within the core of a simple optical fibre by a) Refraction b) Total internal reflection c) reflection d) none of these ans :> b

10) Transmission media are usually categorized as _______. A) Fixed or unfixed B) guided or unguided C) determinate or indeterminate

D) metallic or non-metallic Ans B 11) Transmission media lie below the _______ layer. A) Physical B)network C)transport D)application Ans A 12) _______ cable consists of an inner copper core and a second conducting outer sheath. A) Twisted-pair B)Coaxial C) Fibre-optic D)Shielded twisted-pair Ans B 13) In fibre optics, the signal is _______ waves. A) light B)radio C)infrared D)very low-frequency Ans A 14) Which of the following primarily uses guided media? A) cellular telephone system B)local telephone system C)satellite communications D)radio broadcasting Ans B 15) Which of the following is not a guided medium? A)twisted-pair cable B)coaxial cable C)fiber-optic cable D)atmosphere Ans D

16) What is the major factor that makes coaxial cable less susceptible to noise than twistedpair cable? A)inner conductor B)diameter of cable C)outer conductor D)insulating material Ans C 17) In an optical fiber, the inner core is _______ the cladding. A) denser than B)less dense than C)the same density as D)rarer ANs A 18) The inner core of an optical fiber is _______ in composition. A) glass or plastic B)gas C)plasma D)liquid Ans A 19) When a beam of light travels through media of two different densities, if the angle of incidence is greater than the critical angle, _______ occurs. A) reflection B) diffraction C)incidence D) interference Ans A When the angle of incidence is _______ the critical angle, the light beam bends along the interface. A) more than B)less than C)equal to D)none of the above Ans C 20) Signals with a frequency below 2 MHz use _______ propagation. A)ground B)sky C)line-of-sight D)none of the above Ans A 21) Signals with a frequency between 2 MHz and 30 MHz use ______ propagation. A)ground B)sky C)line-of-sight D)none of the above Ans B

22)Signals with a frequency above 30 MHz use _______propagation. A)ground B)sky C)line-of-sight D)none of the above Ans C 24)______ cables carry data signals in the form of light. A)Coaxial B)Fibre-optic C)Twisted-pair D)none of the above Ans B 25)In a fibre-optic cable, the signal is propagated along the inner core by _______. A) reflection B)refraction C)modulation D)none of the above Ans A 26)_________ media transport electromagnetic waves without the use of a physical conductor. A) Guided B) Unguided C)Either (a) or (b) D)None of the above Ans B 27) Radio waves are _________. A) Omnidirectional B) unidirectional C) bidirectional D) none of the above Ans A 28) Microwaves are _________. A) Omnidirectional B)unidirectional C)bidirectional D)none of the above 29)_______ are used for cellular phone, satellite, and wireless LAN communications.

A)Radio waves B)Microwaves C)Infrared waves D)none of the above Ans B

Intermodal dispersion occurs in a)multimode fibre b)single mode c)both a and b d)none of these Maximum number of modes supported by a graded index fibre is a)(VxV)/2 b)V/2 c)(VxV)/4 d)V/4 Dispersion loss is defined as the spreading of ________propagating through optical fibres. a)light pulse b)sound pulse c)both a and b d)none of these Modal dispersion in an SMSI fibre is a) b) c) d)

greater than MMSI fibre equal to MMSI fibre very less than MMSI fibre none of these

In an optical fibre, dispersion means a)pulse distortion b)pulse narrowing

c)pulse broadening d)pulse rise time

Acceptance angle is maximum for a filter, when e) f) g) h)

critical angle is minimum critical angle is maximum critical angle is zero critical angle is negative

In an optical fiber, propagation angle of light must be equal to or less than a)acceptance angle b)incident angle c)critical angle d)refraction

The total internal reflection takes place when light travels from a)rarer to denser medium b)denser to rarer medium c)air to glass d)glass to air

The main energy loss in optical fiber consists of a)material loss b)scattering loss c)bending loss d)all of these The reduction in the amplitude and intensity of a signal as it is guided through an optical fibre is known as a)dispersion b)diffraction c)attenuation d)diffusion

For long distance communications, which fiber is used? a)single mode b)multimode c)bimode d)all of these

The outer most section of the optical fibre is known as a)core b)cladding c)jacket d)none of these What are the applications of optical fibres? i) j) k) l)

Light weight Flexible Low loss All of these

What are the applications of optical fibres? m) n) o) p)

Light weight Flexible Low loss All of these...