1 $What is the full form of LASER?$

A.

Light Absorption by Stimulated Emission of Radiation

B.

Light Amplification by Spontaneous Emission of Radiation

C.

Light Amplification 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.

Population Inversion

C.

Spontaneous Emission

D.

Stimulated Absorption

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

A.

Stimulated Absorption

B.

Spontaneous Emission

C.

Spontaneous Absorption

D.

Stimulated Emission

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.

Transition time

D.

Pumping 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.

Ground State Saturation

B.

Thermal Equilibrium

C.

Population Inversion

D.

Optical Pumping

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

A.

Stimulated Absorption

B.

Non-radiative decay

C.

Stimulated Emission

D.

Spontaneous Emission

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.

Cooling System

B.

Active Medium

C.

Optical Resonator (Cavity)

D.

Pumping Source

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

A.

Attenuation

B.

Resonance

C.

Pumping

D.

Emission

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

A.

Chemical Pumping

B.

Optical Pumping

C.

Direct Current Injection

D.

Electrical Discharge

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

A.

Inelastic Atom-Atom Collision (Electrical Discharge)

B.

Optical Pumping

C.

Chemical Reaction

D.

Heat Injection

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

A.

Aluminum atoms

B.

Neodymium ions ()

C.

Garnet crystal lattice

D.

Yttrium atoms

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

A.

5-level

B.

3-level

C.

2-level

D.

4-level

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

A.

1.064

B.

694.3 nm

C.

10.6

D.

632.8 nm

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

A.

Krypton

B.

Neon

C.

Helium

D.

Argon

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

A.

694.3 nm

B.

532 nm

C.

1064 nm

D.

632.8 nm

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

A.

Cool the system

B.

Pump the Helium atoms

C.

Provide the mechanical structure

D.

Act as the active centers for lasing

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

A.

1:10

B.

100:1

C.

1:1

D.

10:1

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

A.

It always emits in the UV range

B.

It requires a flash lamp for pumping

C.

Active medium is a P-N junction

D.

It is very large and bulky

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

A.

Forward Biasing

B.

Heating

C.

Reverse Biasing

D.

Optical Pumping

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

A.

Atomic collisions

B.

Recombination of electrons and holes

C.

Rotational transitions

D.

Vibrational transitions

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

A.

Cadmium Sulfide (CdS)

B.

Germanium (Ge)

C.

Gallium Arsenide (GaAs)

D.

Silicon (Si)

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

A.

The doping concentration only

B.

The voltage applied

C.

The bandgap energy of the material

D.

The length of the cavity

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

A.

Directionality (low divergence)

B.

Coherence

C.

Intensity

D.

Monochromaticity

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

A.

Polarization

B.

Intensity

C.

Spatial Coherence

D.

Temporal Coherence

29 $What is Holography?$

A.

A method to measure light intensity

B.

A technique of 2D photography

C.

A method of X-ray imaging

D.

A technique of lensless 3D photography

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

A.

Wavelength; Intensity

B.

Amplitude; Phase and Amplitude

C.

Phase; Amplitude

D.

Frequency; Phase

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

A.

Polarization

B.

Refraction

C.

Diffraction

D.

Interference

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

A.

White light

B.

Polychromatic light

C.

Incoherent light

D.

Highly Coherent light (Laser)

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

A.

Mirror

B.

Diffraction Grating

C.

Prism

D.

Concave Lens

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 requires no pumping

B.

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

C.

It operates at lower frequencies

D.

It uses less expensive mirrors

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

A.

High Monochromaticity

B.

High Intensity

C.

High Coherence

D.

High Divergence

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.

Cooling the cavity

B.

Extracting the laser output

C.

Injecting the pump energy

D.

Stopping the laser

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

A.

The diameter of the laser tube

B.

The energy difference between the lasing levels

C.

The intensity of the pumping source

D.

The length of the laser tube

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

A.

Nitrogen Laser

B.

He-Ne Laser

C.

All lasers are pulsed

D.

Ruby Laser

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

A.

Barcode scanning

B.

Material processing (cutting, welding)

C.

Fiber optic communication (at 1550nm)

D.

CD players

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

A.

Variable depending on time

B.

Ideally infinite

C.

Very broad

D.

Extremely narrow

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

A.

External to the diode

B.

Very thin ()

C.

Made of gas

D.

Very thick ()

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

A.

Too small

B.

High threshold current density

C.

Works only in vacuum

D.

Low power consumption

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 dominates, making lasing difficult

B.

It is very easy to build them

C.

Spontaneous emission is negligible

D.

Stimulated emission is not required

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

A.

4-level solid state laser

B.

3-level solid state laser

C.

Semiconductor laser

D.

Gas laser

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

A.

Tattoo removal

B.

Data storage (Holographic memory)

C.

Hair removal

D.

Laser cutting

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

A.

The image becomes inverted

B.

Each piece contains the whole image (with reduced resolution)

C.

Only part of the image is seen

D.

The image disappears

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

A.

Wien's Displacement Law

B.

Stefan-Boltzmann Law

C.

Rayleigh-Jeans Law

D.

Planck's Radiation Law

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

A.

Zero

B.

Unrelated

C.

Equal

D.

Infinite

Unit 2 - Practice Quiz