Quiz — MPY301

Q1. LASER is an acronym for:

A. Light Amplification by Stimulated Emission of Radiation B. Light Absorption by Stimulated Emission of Radiation C. Light Amplification by Spontaneous Emission of Radiation D. Linear Amplification by Stimulated Emission of Rays

Q2. Stimulated emission produces a photon that is:

A. Random in phase and direction B. Identical in phase, frequency, polarization and direction to the incident photon C. Always of shorter wavelength D. Immediately re-absorbed

Q3. The Einstein coefficient A21 governs:

A. Absorption rate B. Spontaneous emission rate C. Stimulated emission rate only D. Thermal conductivity

Q4. For laser action, the medium must exhibit:

A. Thermal equilibrium of populations B. Population inversion C. Equal populations in all levels D. Zero absorption coefficient

Q5. A two-level system, pumped as hard as possible, can at best achieve:

A. Full population inversion B. Equal populations in the two levels (no net inversion) C. Negative absolute temperature only in theory D. Complete depopulation of the ground state

Q6. A three-level laser system (e.g. Ruby) is generally:

A. More efficient than a four-level system B. Less efficient, and typically operates in pulsed mode C. Impossible to construct D. Only usable for gas lasers

Q7. A four-level laser system is advantageous because:

A. The lower laser level is above the ground state and empties quickly B. It requires no pumping C. It cannot achieve population inversion D. It only works at cryogenic temperatures

Q8. The function of an optical cavity (resonator) in a laser is to:

A. Absorb unwanted photons completely B. Provide feedback and select specific modes to build up coherent output C. Cool the gain medium D. Convert light into heat

Q9. Temporal coherence of a laser beam is associated with:

A. Narrow spectral linewidth / long coherence length B. Beam divergence only C. Beam colour only D. Pump power only

Q10. Spatial coherence of a laser beam allows it to:

A. Diverge rapidly B. Be focused to a very small, tight spot C. Lose polarization D. Increase in wavelength

Q11. CW lasers, unlike pulsed lasers, operate:

A. Only for microseconds B. Continuously, delivering a steady output C. Only underwater D. Only at cryogenic temperature

Q12. The Ruby laser gain medium consists of:

A. Nd³⁺ ions in YAG B. Cr³⁺ ions in an Al₂O₃ (sapphire) host C. Ne gas in a glass tube D. GaAs semiconductor junction

Q13. The Ruby laser emits at a wavelength of approximately:

A. 1064 nm B. 694.3 nm C. 632.8 nm D. 10.6 μm

Q14. The Nd:YAG laser typically emits at:

A. 694.3 nm B. 1064 nm C. 10.6 μm D. 532 nm always

Q15. In the He-Ne laser, population inversion in neon is achieved mainly through:

A. Direct optical pumping of neon B. Near-resonant collisional energy transfer from excited helium atoms C. Chemical reaction with oxygen D. Cooling to liquid helium temperature

Q16. The He-Ne laser's principal red output is at:

A. 532 nm B. 632.8 nm C. 694.3 nm D. 10.6 μm

Q17. The CO2 laser, a molecular gas laser, is notable for:

A. Very low output power B. Very high output power, widely used in industrial cutting C. Only emitting in the visible range D. Being a three-level system

Q18. Excimer lasers use molecules that:

A. Exist stably only in the ground state B. Exist as bound molecules only in an excited electronic state C. Never dissociate D. Only lase in the infrared

Q19. Excimer lasers are widely used in:

A. Deep-sea exploration B. UV photolithography and laser eye surgery (LASIK) C. Radio broadcasting D. Only audio recording

Q20. Dye (liquid) lasers are valued for their:

A. Fixed, single-wavelength output B. Wide tunability across the visible spectrum C. Extremely low cost of dye replacement D. Solid-state gain medium

Q21. A semiconductor (diode) laser generates light through:

A. Nuclear fission B. Electron-hole recombination at a forward-biased p-n junction C. Chemical combustion D. Magnetic resonance

Q22. Fibre lasers use as their gain medium:

A. A rare-earth-doped optical fibre B. A ruby crystal C. Neon gas D. Liquid nitrogen

Q23. Holography differs from ordinary photography because a hologram records:

A. Only the intensity of light B. Both amplitude and phase of the scattered light C. Only the colour of light D. Nothing about the object

Q24. Reconstruction of a hologram requires illumination with:

A. Any random light source B. A beam resembling the original reference beam C. Only sunlight D. Ultrasonic waves

Q25. HNDT (Holographic Non-Destructive Testing) is used to:

A. Destroy a component to test its strength B. Detect surface deformation/defects without damaging the component C. Measure the speed of light D. Amplify a laser beam

Q26. Holographic data storage achieves high density mainly by:

A. Storing data only on the surface B. Using the volume of the medium via angular/wavelength multiplexing C. Reducing the wavelength of visible light to zero D. Using magnetic tape

Q27. Optical fibres guide light along the core primarily due to:

A. Diffraction at the cladding B. Total internal reflection at the core-cladding boundary C. Absorption by the cladding D. Gravity

Q28. A single-mode fibre, compared to a multimode fibre, generally offers:

A. Lower bandwidth and higher dispersion B. Higher bandwidth over long distances due to reduced modal dispersion C. No advantage at all D. Only mechanical strength

Q29. An Erbium-Doped Fibre Amplifier (EDFA) amplifies signals:

A. By converting them to electrical form first B. Directly in the optical domain without opto-electronic conversion C. Only at microwave frequencies D. By reducing their wavelength

Q30. Fibre-optic sensors are valued for being:

A. Highly susceptible to electromagnetic interference B. Immune to electromagnetic interference and remotely operable C. Only usable in vacuum D. Unable to sense temperature

Q31. Saturation spectroscopy is used to achieve:

A. Doppler-broadened spectral lines only B. Doppler-free (sub-Doppler) resolution via a Lamb dip C. Increased Doppler broadening D. Complete extinction of the spectral line

Q32. The 'Lamb dip' observed in saturation spectroscopy arises from:

A. A malfunctioning laser B. Saturation of a velocity subgroup of atoms resonant with the pump beam C. Random detector noise D. Thermal expansion of the sample

Q33. Non-linear spectroscopy exploits high laser intensities to enable:

A. Single-photon linear absorption only B. Multi-photon and non-linear optical processes C. Complete transparency of all media D. Removal of all spectral lines

Q34. Time-domain (pump-probe) spectroscopy with ultrafast lasers is used to study:

A. Static equilibrium properties only B. Real-time dynamics of chemical reactions and carrier relaxation C. Only the speed of sound D. DC electrical resistance

Q35. Stimulated Raman emission produces an output that is:

A. Stokes-shifted relative to the pump via inelastic scattering B. Always at exactly the pump wavelength C. Unrelated to the pump wavelength D. Only observed in solids

Q36. Laser fusion (inertial confinement fusion) works by:

A. Cooling a fuel pellet to absolute zero B. Symmetrically compressing and heating a fuel pellet with many high-power laser beams C. Passing DC current through a plasma only D. Using magnetic fields exclusively

Q37. LASIK eye surgery commonly uses which type of laser?

A. CO2 laser B. Excimer laser C. Ruby laser only D. Fibre laser only

Q38. Photodynamic therapy uses laser light to:

A. Selectively activate a photosensitising drug to destroy targeted cells B. Cool body tissue C. Generate X-rays inside the body D. Replace chemotherapy entirely in all cases

Q39. Laser cutting/drilling achieves precision mainly because the beam:

A. Delivers highly localized, controllable energy to vaporize/melt material B. Cannot be focused at all C. Requires physical contact with the material D. Only works on transparent materials

Q40. Laser welding is characterized by:

A. Wide heat-affected zones and shallow welds B. Deep, narrow welds with low thermal distortion C. No melting of the material at all D. Only being usable on plastics

Q41. Laser alloying is used to:

A. Remove material completely B. Melt a surface layer together with an alloying element to modify local surface properties C. Cut a workpiece into halves D. Measure hardness directly

Q42. Laser Chemical Vapour Deposition (LCVD) is used to:

A. Deposit thin films/microstructures at precisely controlled locations by decomposing precursor gases B. Etch material using acid only C. Increase a component's mass randomly D. Measure optical fibre attenuation

Q43. Laser hardening improves wear resistance in metal components mainly by:

A. Melting the entire component uniformly B. Rapidly heating a thin surface layer followed by rapid self-quenching to form a hard layer C. Cooling the component in liquid nitrogen for a week D. Coating it with paint

Q44. Laser annealing in semiconductor processing is used to:

A. Melt the entire wafer B. Relieve stress or activate dopants without melting the bulk material C. Increase wafer thickness D. Remove all dopants

Q45. LIDAR determines distance to a target by measuring:

A. The colour of the reflected beam only B. The round-trip time of a laser pulse reflected from the target C. The target's temperature D. The target's magnetic field

Q46. LIDAR is commonly used in:

A. Autonomous vehicle navigation and topographic mapping B. Only underwater communication C. Only radio broadcasting D. Only audio recording

Q47. A laser used for industrial cutting of metals is most commonly a:

A. He-Ne laser B. High-power CO2 or fibre laser C. Dye laser D. Excimer laser only

Q48. Which property is essential for a laser beam to remain narrow over long distances (e.g. LIDAR)?

A. High divergence B. Low divergence (high spatial coherence) C. Low temporal coherence D. High absorption in air

Q49. Photolithography in microchip manufacturing typically relies on which type of laser for its short wavelength?

A. Ruby laser B. Excimer laser (deep UV) C. He-Ne laser D. Fibre laser

Q50. The mode-locking technique in lasers is primarily used to generate:

A. Continuous, unmodulated output only B. Ultrashort (pico/femtosecond) pulses by fixing the phase relationship between cavity modes C. Only a single, very long pulse lasting hours D. Purely incoherent light

MPY30150-Question MCQ Quiz