1 $What is the full form of LASER?$

A.

Light Amplification by Stimulated Emission of Radiation

B.

Light Amplification by Spontaneous Emission of Radiation

C.

Light Absorption by Stimulated Emission of Radiation

D.

Light Absorption by Spontaneous Emission of Radiation

2 $In the context of light-matter interaction, what is the process where an atom in the ground state absorbs a photon and moves to an excited state?$

A.

Stimulated Emission

B.

Spontaneous Emission

C.

Stimulated Absorption

D.

Population Inversion

3 $Which process is responsible for the output of a laser beam having high coherence?$

A.

Spontaneous Absorption

B.

Spontaneous Emission

C.

Stimulated Emission

D.

Stimulated Absorption

4 $The average time an atom spends in an excited state before undergoing spontaneous emission is known as:$

A.

Coherence time

B.

Lifetime of the state

C.

Pumping time

D.

Transition time

5 $What is the typical lifetime of an atom in a metastable state ?$

A.

seconds

B.

seconds

C.

seconds

D.

seconds

6 $According to Boltzmann's distribution law, the population ratio of two energy levels at thermal equilibrium is given by:$

A.

B.

C.

D.

7 $What is the condition called where the number of atoms in a higher energy state () exceeds the number of atoms in a lower energy state ()?$

A.

Thermal Equilibrium

B.

Population Inversion

C.

Optical Pumping

D.

Ground State Saturation

8 $The Einstein coefficient represents the probability per unit time of which process?$

A.

Stimulated Absorption

B.

Stimulated Emission

C.

Spontaneous Emission

D.

Non-radiative decay

9 $What is the relationship between the Einstein coefficients for stimulated absorption () and stimulated emission ()?$

A.

B.

C.

D.

10 $The ratio of Spontaneous Emission rate to Stimulated Emission rate () is proportional to:$

A.

B.

C.

D.

11 $Which component of a laser system is responsible for providing the necessary positive feedback to sustain oscillations?$

A.

Active Medium

B.

Pumping Source

C.

Optical Resonator (Cavity)

D.

Cooling System

12 $The process of supplying energy to the active medium to achieve population inversion is called:$

A.

Emission

B.

Pumping

C.

Resonance

D.

Attenuation

13 $Which pumping method is primarily used in the Nd:YAG laser?$

A.

Electrical Discharge

B.

Optical Pumping

C.

Chemical Pumping

D.

Direct Current Injection

14 $Which pumping method is primarily used in the He-Ne laser?$

A.

Optical Pumping

B.

Inelastic Atom-Atom Collision (Electrical Discharge)

C.

Chemical Reaction

D.

Heat Injection

15 $The active medium in an Nd:YAG laser is:$

A.

Yttrium atoms

B.

Aluminum atoms

C.

Neodymium ions ()

D.

Garnet crystal lattice

16 $Nd:YAG laser is an example of a____laser.$

A.

2-level

B.

3-level

C.

4-level

D.

5-level

17 $The characteristic output wavelength of an Nd:YAG laser is:$

A.

632.8 nm

B.

1.064

C.

694.3 nm

D.

10.6

18 $In the He-Ne laser, which element provides the metastable state required for energy transfer?$

A.

Neon

B.

Helium

C.

Argon

D.

Krypton

19 $The visible red light emitted by a He-Ne laser has a wavelength of:$

A.

532 nm

B.

632.8 nm

C.

694.3 nm

D.

1064 nm

20 $In a He-Ne laser, the role of the Neon atoms is to:$

A.

Provide the mechanical structure

B.

Act as the active centers for lasing

C.

Cool the system

D.

Pump the Helium atoms

21 $What is the typical ratio of Helium to Neon in a He-Ne gas laser?$

A.

1:10

B.

10:1

C.

1:1

D.

100:1

22 $Which of the following is a characteristic property of a Semiconductor Diode Laser?$

A.

It requires a flash lamp for pumping

B.

It is very large and bulky

C.

Active medium is a P-N junction

D.

It always emits in the UV range

23 $The pumping mechanism in a Semiconductor Laser is:$

A.

Forward Biasing

B.

Reverse Biasing

C.

Optical Pumping

D.

Heating

24 $In a semiconductor laser, photon emission occurs due to:$

A.

Atomic collisions

B.

Recombination of electrons and holes

C.

Vibrational transitions

D.

Rotational transitions

25 $Which material is commonly used for fabricating semiconductor lasers emitting in the infrared region?$

A.

Silicon (Si)

B.

Germanium (Ge)

C.

Gallium Arsenide (GaAs)

D.

Cadmium Sulfide (CdS)

26 $The wavelength of light emitted by a semiconductor laser depends primarily on:$

A.

The voltage applied

B.

The bandgap energy of the material

C.

The length of the cavity

D.

The doping concentration only

27 $Which property of laser light implies that the photons travel in a single direction with very little spreading?$

A.

Monochromaticity

B.

Directionality (low divergence)

C.

Coherence

D.

Intensity

28 $The property of a laser beam having a constant phase difference between two points in space at a given time is called:$

A.

Temporal Coherence

B.

Spatial Coherence

C.

Polarization

D.

Intensity

29 $What is Holography?$

A.

A technique of 2D photography

B.

A technique of lensless 3D photography

C.

A method to measure light intensity

D.

A method of X-ray imaging

30 $Ordinary photography records the__of light, while holography records__.$

A.

Phase; Amplitude

B.

Amplitude; Phase and Amplitude

C.

Frequency; Phase

D.

Wavelength; Intensity

31 $The physical principle behind the recording of a hologram is:$

A.

Diffraction

B.

Interference

C.

Polarization

D.

Refraction

32 $What type of light source is strictly required for recording a hologram?$

A.

Polychromatic light

B.

Incoherent light

C.

Highly Coherent light (Laser)

D.

White light

33 $In the reconstruction of a hologram, the hologram acts as a:$

A.

Prism

B.

Diffraction Grating

C.

Concave Lens

D.

Mirror

34 $Which Einstein coefficient is related to the absorption of radiation?$

A.

B.

C.

D.

35 $Why is a 4-level laser generally more efficient than a 3-level laser?$

A.

It uses less expensive mirrors

B.

The terminal laser level is not the ground state, so it is easier to empty

C.

It requires no pumping

D.

It operates at lower frequencies

36 $Which of the following is NOT a property of laser light?$

A.

High Divergence

B.

High Monochromaticity

C.

High Intensity

D.

High Coherence

37 $In an optical resonator, if the reflection coefficient of one mirror is 100% and the other is slightly less (e.g., 98%), the latter is used for:$

A.

Stopping the laser

B.

Injecting the pump energy

C.

Extracting the laser output

D.

Cooling the cavity

38 $The color of the light emitted by a laser is determined by:$

A.

The intensity of the pumping source

B.

The energy difference between the lasing levels

C.

The length of the laser tube

D.

The diameter of the laser tube

39 $Which of the following lasers is capable of continuous wave (CW) operation?$

A.

Ruby Laser

B.

He-Ne Laser

C.

Nitrogen Laser

D.

All lasers are pulsed

40 $A typical application of the Nd:YAG laser is:$

A.

Barcode scanning

B.

Material processing (cutting, welding)

C.

CD players

D.

Fiber optic communication (at 1550nm)

41 $The spectral width (bandwidth) of a laser beam is:$

A.

Ideally infinite

B.

Very broad

C.

Extremely narrow

D.

Variable depending on time

42 $In a homojunction semiconductor laser, the active region is:$

A.

Very thick ()

B.

Very thin ()

C.

External to the diode

D.

Made of gas

43 $What is the primary disadvantage of a homojunction semiconductor laser compared to a heterojunction one?$

A.

High threshold current density

B.

Low power consumption

C.

Too small

D.

Works only in vacuum

44 $Which term describes the constancy of the phase relationship of a wave at a fixed point over a period of time?$

A.

Spatial Coherence

B.

Temporal Coherence

C.

Amplitude Stability

D.

Frequency Stability

45 $In the Einstein relation, what does this imply for UV or X-ray lasers?$

A.

Spontaneous emission is negligible

B.

It is very easy to build them

C.

Spontaneous emission dominates, making lasing difficult

D.

Stimulated emission is not required

46 $The 'Ruby Laser', historically the first laser, is an example of a:$

A.

3-level solid state laser

B.

4-level solid state laser

C.

Gas laser

D.

Semiconductor laser

47 $Which of the following is an application of Holography?$

A.

Laser cutting

B.

Data storage (Holographic memory)

C.

Hair removal

D.

Tattoo removal

48 $When a hologram is cut into pieces, what happens?$

A.

Only part of the image is seen

B.

The image disappears

C.

Each piece contains the whole image (with reduced resolution)

D.

The image becomes inverted

49 $The energy density of radiation in a cavity at thermal equilibrium is given by:$

A.

Rayleigh-Jeans Law

B.

Planck's Radiation Law

C.

Wien's Displacement Law

D.

Stefan-Boltzmann Law

50 $For a system in thermal equilibrium, the rate of upward transitions (absorption) and downward transitions (emission) must be:$

A.

Zero

B.

Equal

C.

Infinite

D.

Unrelated

Unit 2 - Practice Quiz