Q.1 What type of microscopy uses a focused beam of light to scan a specimen and generate an image by collecting the reflected light?
Fluorescence microscopy
Confocal microscopy
Electron microscopy
Phase-contrast microscopy
Explanation - Confocal microscopy uses a laser to scan the specimen point‑by‑point and a pinhole to reject out‑of‑focus light, producing high‑resolution images.
Correct answer is: Confocal microscopy
Q.2 Which imaging technique provides information about the internal structure of a cell by detecting the scattering of electrons?
Transmission electron microscopy
Scanning electron microscopy
Atomic force microscopy
Light microscopy
Explanation - TEM transmits electrons through a thin sample and records the scattered electrons, revealing fine subcellular structures.
Correct answer is: Transmission electron microscopy
Q.3 In fluorescence microscopy, what is the main function of the dichroic mirror?
To focus the excitation light onto the sample
To separate excitation light from emitted fluorescence
To increase the numerical aperture of the objective
To cool the detector sensor
Explanation - The dichroic mirror reflects excitation wavelengths and transmits longer‑wavelength fluorescence, allowing simultaneous illumination and detection.
Correct answer is: To separate excitation light from emitted fluorescence
Q.4 Which parameter of an optical microscope determines the maximum theoretical resolution?
Numerical aperture
Magnification
Working distance
Field of view
Explanation - Resolution is inversely proportional to the numerical aperture; higher NA allows finer detail to be resolved.
Correct answer is: Numerical aperture
Q.5 What is the purpose of using a pinhole in a confocal microscope?
To increase illumination intensity
To block out‑of‑focus light
To reduce photobleaching
To focus the laser beam
Explanation - The pinhole removes light that does not originate from the focal plane, enhancing optical sectioning capability.
Correct answer is: To block out‑of‑focus light
Q.6 Which detector is commonly used in fluorescence microscopy to capture emitted photons?
CCD camera
Photodiode array
Photomultiplier tube
Thermal sensor
Explanation - PMTs provide high sensitivity and fast response, ideal for detecting weak fluorescence signals.
Correct answer is: Photomultiplier tube
Q.7 What is the main advantage of structured illumination microscopy (SIM) over conventional wide‑field fluorescence microscopy?
Higher temporal resolution
Super‑resolution imaging
Simpler sample preparation
Lower phototoxicity
Explanation - SIM doubles the spatial resolution by projecting patterned illumination and computationally reconstructing the image.
Correct answer is: Super‑resolution imaging
Q.8 In scanning electron microscopy (SEM), which mode of detection provides elemental composition information?
Backscattered electron detection
Secondary electron detection
Energy‑dispersive X‑ray spectroscopy (EDX)
Optical photodiode detection
Explanation - EDX detects characteristic X‑rays emitted when the specimen is bombarded by electrons, revealing elemental composition.
Correct answer is: Energy‑dispersive X‑ray spectroscopy (EDX)
Q.9 Which of the following is NOT a common fluorescent dye used for labeling cell membranes?
DiI
FITC
DAPI
Rhodamine B
Explanation - DAPI stains DNA in the nucleus; it is not used for membrane labeling.
Correct answer is: DAPI
Q.10 What is the typical sample thickness requirement for transmission electron microscopy (TEM) to achieve adequate electron transparency?
0.1–1 mm
1–10 µm
50–100 nm
10–100 nm
Explanation - TEM requires very thin samples (10–100 nm) so that electrons can transmit through the specimen.
Correct answer is: 10–100 nm
Q.11 Which image processing technique is most effective for removing Gaussian noise from a cellular image?
Median filtering
Gaussian smoothing
Edge detection
Histogram equalization
Explanation - Gaussian smoothing applies a Gaussian kernel, which matches the statistical properties of Gaussian noise, reducing it while preserving edges.
Correct answer is: Gaussian smoothing
Q.12 In optical coherence tomography (OCT), what is the primary source of axial resolution?
Numerical aperture of the objective lens
Bandwidth of the light source
Magnification of the imaging system
Signal‑to‑noise ratio
Explanation - OCT axial resolution is inversely proportional to the light source bandwidth; broader bandwidth yields finer axial resolution.
Correct answer is: Bandwidth of the light source
Q.13 Which of the following is a major limitation of electron microscopy for live cell imaging?
High cost of equipment
Requirement for vacuum environment
Limited magnification
Short working distance
Explanation - EM needs a high vacuum, making it unsuitable for observing live cells in their natural aqueous environment.
Correct answer is: Requirement for vacuum environment
Q.14 What does the term 'numerical aperture' (NA) describe in a microscope objective?
The maximum magnification achievable
The angular acceptance of light rays by the objective
The depth of field
The color fidelity of the image
Explanation - NA = n sin(θ) where n is refractive index and θ is half the maximum acceptance angle.
Correct answer is: The angular acceptance of light rays by the objective
Q.15 Which fluorescent probe is commonly used to stain the cytoskeleton actin filaments?
Phalloidin conjugated to Alexa Fluor 488
DAPI
FITC‑BSA
Texas Red‑dextran
Explanation - Phalloidin binds specifically to F‑actin and when conjugated to a fluorophore, visualizes the cytoskeleton.
Correct answer is: Phalloidin conjugated to Alexa Fluor 488
Q.16 Which imaging technique uses X‑rays to generate contrast from differences in electron density?
Magnetic resonance microscopy
Computed tomography
Ultrasound microscopy
Optical coherence tomography
Explanation - CT scans use X‑ray attenuation differences to create 3‑D images of internal structures.
Correct answer is: Computed tomography
Q.17 What is the main advantage of light-sheet fluorescence microscopy (LSFM) for live imaging?
High spatial resolution
Reduced phototoxicity
Fast acquisition time
Compatibility with electron microscopy
Explanation - LSFM illuminates only the imaging plane, minimizing out‑of‑focus exposure and photodamage.
Correct answer is: Reduced phototoxicity
Q.18 Which component of a fluorescence microscope is responsible for filtering excitation light before it reaches the sample?
Emission filter
Dichroic mirror
Excitation filter
Objective lens
Explanation - The excitation filter transmits only the desired wavelength range to the sample.
Correct answer is: Excitation filter
Q.19 In confocal microscopy, how is the optical section thickness related to the pinhole size?
Directly proportional
Inversely proportional
Independent
Square of the pinhole size
Explanation - A smaller pinhole yields thinner optical sections but reduces signal intensity.
Correct answer is: Inversely proportional
Q.20 Which of the following best describes the principle of photo‑acoustic microscopy (PAM)?
Conversion of absorbed light to acoustic waves for imaging
Detection of emitted fluorescence photons
Measurement of electron scattering patterns
Imaging via X‑ray absorption differences
Explanation - PAM uses pulsed laser excitation to generate thermo‑acoustic signals that are detected by ultrasound transducers.
Correct answer is: Conversion of absorbed light to acoustic waves for imaging
Q.21 What is the typical numerical aperture range for high‑resolution wide‑field fluorescence objectives?
0.15–0.30
0.50–0.60
0.80–1.30
1.50–2.00
Explanation - High‑NA objectives (0.80–1.30) provide better resolution and light gathering for fluorescence imaging.
Correct answer is: 0.80–1.30
Q.22 Which of these techniques is used to quantify the number of fluorescent molecules in a single cell?
Fluorescence lifetime imaging microscopy (FLIM)
Quantitative fluorescence microscopy (QFM)
Laser scanning confocal microscopy
Dark‑field microscopy
Explanation - QFM calibrates fluorescence intensity to known standards, enabling absolute molecule counting.
Correct answer is: Quantitative fluorescence microscopy (QFM)
Q.23 What is the purpose of deconvolution in digital image processing of microscopic images?
To sharpen edges by edge detection
To reduce the effect of out‑of‑focus blur
To enhance color contrast
To compress image size
Explanation - Deconvolution algorithms model the point spread function and reverse blur, improving resolution.
Correct answer is: To reduce the effect of out‑of‑focus blur
Q.24 Which microscopy modality provides 3‑D imaging with sub‑micron lateral resolution and nanometer axial resolution?
Atomic force microscopy (AFM)
Super‑resolution structured illumination microscopy (SIM)
Scanning tunneling microscopy (STM)
Transmission electron microscopy (TEM)
Explanation - TEM delivers sub‑nanometer resolution in both lateral and axial dimensions for thin biological samples.
Correct answer is: Transmission electron microscopy (TEM)
Q.25 Which of the following best describes a photomultiplier tube’s (PMT) working principle?
Conversion of light into electrical current via a semiconductor photodiode
Amplification of photoelectrons through a dynode cascade
Conversion of light into heat measured by a bolometer
Direct measurement of photon energy by a calorimeter
Explanation - PMTs multiply the initial photoelectron signal across several dynodes, yielding a detectable current.
Correct answer is: Amplification of photoelectrons through a dynode cascade
Q.26 In fluorescence resonance energy transfer (FRET), what is required for energy transfer to occur?
Large distance between donor and acceptor (>100 nm)
Spectral overlap and close proximity (<10 nm)
Different excitation wavelengths
High temperature
Explanation - FRET efficiency depends on donor emission overlapping acceptor absorption and a very short distance between them.
Correct answer is: Spectral overlap and close proximity (<10 nm)
Q.27 Which component of an electron microscope is responsible for focusing the electron beam onto the sample?
Electrostatic lenses
Magnetic lenses
Apertures
Coils
Explanation - Electron microscopes use magnetic lenses to control and focus the high‑energy electron beam.
Correct answer is: Magnetic lenses
Q.28 What is the typical working distance of a high‑NA water‑immersion objective used in live‑cell imaging?
0.5–1 mm
1–3 mm
3–5 mm
5–10 mm
Explanation - Water‑immersion objectives have short working distances (≈1–3 mm) suitable for live‑cell imaging.
Correct answer is: 1–3 mm
Q.29 Which of the following is a key advantage of using a high‑speed sCMOS camera in fluorescence microscopy?
Higher sensitivity to single photons
Lower read‑out noise
Faster acquisition rates with large fields of view
Better spectral resolution
Explanation - sCMOS cameras combine high pixel counts with rapid frame rates, enabling dynamic live‑cell imaging.
Correct answer is: Faster acquisition rates with large fields of view
Q.30 Which microscopy technique directly visualizes the 3‑D topology of a living cell surface?
Scanning electron microscopy
Atomic force microscopy
Confocal laser scanning microscopy
Transmission electron microscopy
Explanation - AFM uses a mechanical probe to map surface topography in real‑time, even in aqueous environments.
Correct answer is: Atomic force microscopy
Q.31 What is the primary function of an immersion oil in bright‑field microscopy?
To increase the numerical aperture by matching refractive indices
To reduce chromatic aberration
To fix the sample
To act as a fluorescent dye
Explanation - Immersion oil reduces light refraction at the glass interface, improving NA and resolution.
Correct answer is: To increase the numerical aperture by matching refractive indices
Q.32 Which imaging modality uses a combination of light and magnetic resonance to achieve high‑contrast images of cellular components?
Optical coherence tomography
Magnetic resonance microscopy (MRM)
Photo‑acoustic microscopy
Ultrasound microscopy
Explanation - MRM uses magnetic fields and radiofrequency pulses, producing high‑contrast images without ionizing radiation.
Correct answer is: Magnetic resonance microscopy (MRM)
Q.33 In a fluorescence microscope, what is the consequence of using an excitation wavelength that is too short for the fluorophore?
Reduced photobleaching
Enhanced signal intensity
Quenching of fluorescence due to photodamage
No effect on imaging
Explanation - Exciting too high an energy can damage the fluorophore, decreasing emission intensity.
Correct answer is: Quenching of fluorescence due to photodamage
Q.34 What is the role of a neutral density (ND) filter in a laser scanning microscope?
To change the wavelength of the laser
To block fluorescence emission
To reduce laser power without changing beam profile
To polarize the excitation light
Explanation - ND filters attenuate intensity uniformly, protecting the sample from photodamage.
Correct answer is: To reduce laser power without changing beam profile
Q.35 Which of the following is NOT a type of light source used in confocal microscopy?
Diode laser
Tungsten‑halogen lamp
Solid‑state laser
Supercontinuum laser
Explanation - Confocal systems typically use coherent laser sources; tungsten‑halogen lamps are for wide‑field imaging.
Correct answer is: Tungsten‑halogen lamp
Q.36 In the context of super‑resolution microscopy, what does the term 'dye blinking' refer to?
Continuous emission of photons
Fluorophore switching between on/off states
Photobleaching of the dye
Spectral shift of emission
Explanation - Blinking allows sparse activation of molecules for techniques like PALM/STORM.
Correct answer is: Fluorophore switching between on/off states
Q.37 Which imaging principle allows optical coherence tomography to achieve micron‑scale depth resolution?
Holographic interference
Speckle contrast
Low coherence interferometry
Photon counting
Explanation - Using short‑coherence light restricts interference to a small depth range, granting high axial resolution.
Correct answer is: Low coherence interferometry
Q.38 Which of the following is a typical challenge when imaging thick tissue sections with fluorescence microscopy?
Chromatic aberration
Photobleaching
Out‑of‑focus light scattering
Limited numerical aperture
Explanation - Thick specimens scatter light, reducing contrast; optical sectioning or clearing is required.
Correct answer is: Out‑of‑focus light scattering
Q.39 Which of the following is a key advantage of using a water‑immersion objective over an oil‑immersion objective for live‑cell imaging?
Higher numerical aperture
Reduced phototoxicity
Simpler sample mounting
Better depth of field
Explanation - Water immersion eliminates the need for immersion oil and reduces contamination of the sample.
Correct answer is: Simpler sample mounting
Q.40 Which of the following techniques is primarily used to visualize the electrical activity of a cell at the subcellular level?
Calcium imaging
Electron microscopy
Phase‑contrast microscopy
Bright‑field microscopy
Explanation - Calcium indicators fluoresce upon binding Ca²⁺, revealing dynamic electrical events.
Correct answer is: Calcium imaging
Q.41 What is the main purpose of using a condenser in a fluorescence microscope?
To focus the emitted fluorescence onto the detector
To provide a high‑NA light source for excitation
To collimate the illumination beam
To filter out unwanted wavelengths
Explanation - The condenser collects and focuses the excitation light onto the specimen, increasing illumination efficiency.
Correct answer is: To provide a high‑NA light source for excitation
Q.42 In digital pathology, what is the typical resolution limit of whole‑slide scanners used for histology?
1–5 µm
10–20 µm
0.5–1 µm
5–10 µm
Explanation - Whole‑slide scanners often achieve sub‑micron resolution to preserve cellular detail.
Correct answer is: 0.5–1 µm
Q.43 Which of the following is a common source of autofluorescence in biological specimens?
Hemoglobin
Lipids
Collagen
All of the above
Explanation - Endogenous biomolecules can emit fluorescence, contributing to background signal.
Correct answer is: All of the above
Q.44 What is the primary limitation of using standard optical microscopy for imaging sub‑100 nm structures?
Chromatic aberration
Diffraction limit of light
High phototoxicity
Limited sample thickness
Explanation - Optical resolution is limited to about half the wavelength (~200 nm) due to diffraction.
Correct answer is: Diffraction limit of light
Q.45 Which of the following best describes the 'point spread function' (PSF) in microscopy?
The probability distribution of photon arrival times
The response of the imaging system to a point source
The spectral bandwidth of the illumination
The angular distribution of scattered light
Explanation - PSF characterizes how a point object is imaged, influencing resolution and deconvolution.
Correct answer is: The response of the imaging system to a point source
Q.46 Which type of microscopy is best suited for imaging live bacterial cells in real‑time?
Dark‑field microscopy
Transmission electron microscopy
Scanning electron microscopy
Phase‑contrast microscopy
Explanation - Phase‑contrast enhances contrast in transparent cells without staining, ideal for live imaging.
Correct answer is: Phase‑contrast microscopy
Q.47 What is the main advantage of using a cryo‑TEM for biological samples?
High throughput imaging
Preservation of native structure
Ability to image live cells
Low cost equipment
Explanation - Cryo‑TEM freezes samples rapidly, minimizing artifacts and maintaining native conformations.
Correct answer is: Preservation of native structure
Q.48 Which of the following parameters is NOT typically adjustable in a confocal microscope’s optical sectioning?
Pinhole size
Laser power
Objective magnification
Sample temperature
Explanation - Optical sectioning is controlled by pinhole, laser power, and objective; temperature is independent.
Correct answer is: Sample temperature
Q.49 Which imaging technique uses acoustic waves generated by pulsed light to produce high‑resolution images?
Optical coherence tomography
Photo‑acoustic microscopy
Laser scanning confocal microscopy
Bright‑field microscopy
Explanation - Pulsed light causes rapid thermal expansion, generating acoustic signals detected for imaging.
Correct answer is: Photo‑acoustic microscopy
Q.50 What is the purpose of a 'neutral‑density filter' in a fluorescence imaging setup?
To block reflected light
To adjust the illumination intensity
To split the emitted fluorescence into two colors
To polarize the excitation beam
Explanation - ND filters attenuate light intensity uniformly, protecting fluorophores from photobleaching.
Correct answer is: To adjust the illumination intensity
Q.51 Which of the following is a key feature of stimulated Raman scattering (SRS) microscopy?
Detection of fluorescent tags
Label‑free chemical contrast
High phototoxicity
Requirement for cryogenic temperatures
Explanation - SRS uses vibrational resonances to generate contrast without the need for labels.
Correct answer is: Label‑free chemical contrast
Q.52 What is the main benefit of using a multi‑photon excitation microscope for deep tissue imaging?
Higher photobleaching rate
Lower scattering of excitation light
Requirement of higher laser power
Reduced depth penetration
Explanation - Near‑IR multi‑photon light scatters less, enabling imaging deeper into tissues.
Correct answer is: Lower scattering of excitation light
Q.53 Which of the following best describes the 'optical sectioning' capability of a confocal microscope?
Acquisition of multiple focal planes in rapid succession
Blocking of out‑of‑focus light using a pinhole
Use of a high‑numerical‑aperture objective
Detection of fluorescence lifetime
Explanation - The pinhole rejects light from other planes, creating a thin optical section.
Correct answer is: Blocking of out‑of‑focus light using a pinhole
Q.54 Which of the following is a common method to increase the penetration depth of optical imaging in scattering tissues?
Use of ultraviolet illumination
Use of near‑infrared illumination
Increased numerical aperture
Higher laser power
Explanation - Near‑IR light scatters less in biological tissues, allowing deeper imaging.
Correct answer is: Use of near‑infrared illumination
Q.55 In a fluorescence microscope, which component is responsible for filtering out the excitation light from reaching the detector?
Dichroic mirror
Excitation filter
Emission filter
Objective lens
Explanation - The emission filter transmits fluorescence wavelengths while blocking excitation light.
Correct answer is: Emission filter
Q.56 What is the typical wavelength range for the visible spectrum used in most fluorescence microscopy?
200–400 nm
400–700 nm
700–1100 nm
1100–1500 nm
Explanation - Visible light spans roughly 400–700 nm, within which most fluorophores are excited.
Correct answer is: 400–700 nm
Q.57 Which type of microscope is best suited for imaging sub‑nanometer features in crystalline materials?
Transmission electron microscopy
Confocal laser scanning microscope
Atomic force microscope
Dark‑field microscope
Explanation - TEM provides the resolution needed to observe atomic‑scale structures.
Correct answer is: Transmission electron microscopy
Q.58 Which of the following is NOT a common fluorescent dye used for labeling DNA in microscopy?
DAPI
SYTO 9
Alexa Fluor 647
Propidium iodide
Explanation - Alexa Fluor 647 is a far‑red dye commonly used for protein labeling; it does not preferentially bind DNA.
Correct answer is: Alexa Fluor 647
Q.59 Which parameter primarily determines the axial resolution in a confocal microscope?
Pinhole size
Numerical aperture of the objective
Laser wavelength
Detector quantum efficiency
Explanation - The axial resolution is mainly controlled by the pinhole diameter relative to the Airy disk.
Correct answer is: Pinhole size
Q.60 What is the main advantage of using an adaptive optics system in microscopic imaging?
Compensation for sample-induced aberrations
Increased phototoxicity
Simplified sample mounting
Reduction of laser power
Explanation - Adaptive optics correct distortions caused by refractive index variations in thick samples.
Correct answer is: Compensation for sample-induced aberrations
Q.61 Which of the following best describes 'phase imaging' techniques?
Detection of fluorescence lifetimes
Measurement of optical path length variations
Recording of electron diffraction patterns
Spectral imaging of emitted photons
Explanation - Phase imaging captures differences in phase caused by refractive index variations in transparent specimens.
Correct answer is: Measurement of optical path length variations
Q.62 Which of the following is a typical method for reducing photobleaching in live‑cell fluorescence imaging?
Use of high laser power
Short exposure times
Continuous illumination
High fluorophore concentration
Explanation - Minimizing exposure reduces the total photon dose, limiting photobleaching.
Correct answer is: Short exposure times
Q.63 What is the main purpose of a 'confocal pinhole' in a laser scanning microscope?
To focus the laser onto the sample
To reject out‑of‑focus light
To increase the numerical aperture
To filter the emitted fluorescence
Explanation - The pinhole allows only in‑focus light to reach the detector, improving image contrast.
Correct answer is: To reject out‑of‑focus light
Q.64 Which of the following is a common application of electron tomography in cell biology?
Visualization of subcellular organelle architecture
Imaging of live cellular dynamics
Detection of fluorescent markers
Measuring cell viability
Explanation - Electron tomography reconstructs 3‑D volumes from multiple electron micrographs of thin sections.
Correct answer is: Visualization of subcellular organelle architecture
Q.65 What is a key limitation of using fluorescence lifetime imaging microscopy (FLIM) for subcellular imaging?
Low spatial resolution
Long acquisition times
Requirement for fluorescent labels
Inability to detect spectral shifts
Explanation - FLIM often requires many photon counts per pixel, leading to slower imaging speeds.
Correct answer is: Long acquisition times
Q.66 Which of the following microscopy techniques uses a laser to excite fluorescence in a thin plane and collects the emitted light with a camera?
Spinning disk confocal microscopy
Wide‑field fluorescence microscopy
Bright‑field microscopy
Phase‑contrast microscopy
Explanation - Spinning disk confocal uses multiple pinholes on a rotating disk to achieve fast optical sectioning.
Correct answer is: Spinning disk confocal microscopy
Q.67 Which parameter of a fluorescence microscope determines how quickly a live cell can be imaged?
Numerical aperture
Laser power
Detector readout speed
Emission filter bandwidth
Explanation - Fast detector readout allows rapid frame acquisition, essential for live‑cell dynamics.
Correct answer is: Detector readout speed
Q.68 What does the 'field of view' in a microscope refer to?
The magnification of the objective
The area that can be imaged at one time
The depth of focus
The wavelength range of illumination
Explanation - Field of view is the total visible area of the sample in the image.
Correct answer is: The area that can be imaged at one time
Q.69 Which of the following best describes 'raster scanning' in laser scanning microscopy?
Scanning the laser in a spiral pattern
Scanning the laser linearly across the sample in rows
Scanning the sample in random positions
Simultaneous multi‑spot excitation
Explanation - Raster scanning moves the beam in a systematic line‑by‑line pattern to build an image.
Correct answer is: Scanning the laser linearly across the sample in rows
Q.70 Which type of microscopy is most suitable for imaging the surface topography of living cells in aqueous solutions?
Scanning electron microscopy
Atomic force microscopy
Transmission electron microscopy
Confocal microscopy
Explanation - AFM operates in liquid environments, measuring forces on the sample surface without vacuum.
Correct answer is: Atomic force microscopy
Q.71 What is the main purpose of using a 'fluorescence filter cube' in a microscope?
To adjust the focus of the objective
To separate excitation and emission light paths
To increase magnification
To enhance chromatic aberration
Explanation - A filter cube contains the excitation filter, dichroic mirror, and emission filter.
Correct answer is: To separate excitation and emission light paths
Q.72 Which of the following is a major drawback of using wide‑field fluorescence microscopy for thick specimens?
Low resolution
Out‑of‑focus background
High photobleaching
Limited spectral range
Explanation - Wide‑field captures all planes simultaneously, causing background from out‑of‑focus light.
Correct answer is: Out‑of‑focus background
Q.73 Which of the following microscopy methods provides chemical composition information without labels?
Raman microscopy
Fluorescence microscopy
Confocal microscopy
Bright‑field microscopy
Explanation - Raman spectroscopy detects vibrational modes of molecules, revealing chemical identity.
Correct answer is: Raman microscopy
Q.74 What does the 'depth of field' (DOF) describe in an optical system?
The thickness of the focal plane that remains sharp
The maximum magnification achievable
The range over which the detector can resolve different colors
The distance between the objective and the sample
Explanation - DOF is the axial range over which the image is acceptably in focus.
Correct answer is: The thickness of the focal plane that remains sharp
Q.75 Which of the following is an advantage of using a water‑immersion objective over an air objective for deep imaging?
Higher numerical aperture
Reduced scattering in thick samples
Simpler mounting procedure
Lower phototoxicity
Explanation - Water immersion matches refractive indices better, allowing higher NA and better resolution.
Correct answer is: Higher numerical aperture
Q.76 What is the primary reason for using a 'tandem microscope' in live‑cell imaging?
Combining bright‑field with fluorescence for simultaneous imaging
Using two objectives simultaneously
Providing higher magnification
Enabling electron detection in the same platform
Explanation - Tandem microscopes allow overlaying of bright‑field and fluorescence images in real‑time.
Correct answer is: Combining bright‑field with fluorescence for simultaneous imaging
Q.77 Which of the following best explains the concept of 'photon shot noise' in microscopy?
Noise due to fluctuations in laser output power
Random fluctuations in the number of detected photons
Thermal noise from the detector electronics
Electronic interference from surrounding equipment
Explanation - Shot noise arises from the quantum nature of light, causing variance in photon counts.
Correct answer is: Random fluctuations in the number of detected photons
Q.78 In super‑resolution STED microscopy, which component is responsible for de‑exciting fluorophores in the periphery of the excitation spot?
Excitation laser
STED depletion beam
Emission filter
Detector
Explanation - The STED beam de‑excites peripheral fluorophores, shrinking the effective emission spot.
Correct answer is: STED depletion beam
Q.79 Which of the following best describes the 'confocal pinhole' size effect on image brightness?
Smaller pinhole increases brightness
Smaller pinhole decreases brightness
Pinhole size has no effect
Larger pinhole decreases brightness
Explanation - A smaller pinhole blocks more light, reducing signal intensity while improving sectioning.
Correct answer is: Smaller pinhole decreases brightness
Q.80 What is the main advantage of using a 'multicolor imaging' setup in cellular microscopy?
Increased magnification
Simultaneous visualization of multiple cellular components
Reduced photobleaching
Lower cost of reagents
Explanation - Multicolor imaging allows labeling and detection of several targets concurrently.
Correct answer is: Simultaneous visualization of multiple cellular components
Q.81 Which type of microscopy is used to directly observe the crystalline lattice of a biomineralized tissue?
Bright‑field microscopy
Scanning electron microscopy
Transmission electron microscopy
Confocal microscopy
Explanation - TEM can resolve crystal lattices in thin sections of mineralized tissues.
Correct answer is: Transmission electron microscopy
Q.82 What is the purpose of using a 'spherical aberration correction collar' in a microscope objective?
To adjust magnification
To reduce distortion due to refractive index mismatch
To enhance fluorescence intensity
To stabilize the optical path
Explanation - The correction collar compensates for sample thickness and immersion medium differences.
Correct answer is: To reduce distortion due to refractive index mismatch
Q.83 Which of the following is a common fluorophore used for labeling mitochondria?
FITC
MitoTracker Red
DAPI
Alexa Fluor 488
Explanation - MitoTracker Red selectively accumulates in active mitochondria, emitting bright red fluorescence.
Correct answer is: MitoTracker Red
Q.84 Which of the following best describes the function of a 'camera-based detector' in a modern microscope?
To amplify the excitation laser
To collect and record emitted light as a digital image
To filter out background light
To provide optical sectioning
Explanation - Cameras convert photon flux into digital pixel values for analysis.
Correct answer is: To collect and record emitted light as a digital image
Q.85 What is the main advantage of 'dual‑channel' imaging in a confocal microscope?
Increased magnification
Simultaneous imaging of two fluorophores
Reduced phototoxicity
Simplified optical path
Explanation - Dual‑channel detectors enable real‑time comparison of two labeled targets.
Correct answer is: Simultaneous imaging of two fluorophores
Q.86 Which of the following best describes the term 'photobleaching'?
The loss of fluorescence due to prolonged exposure to light
The increase in fluorescence signal over time
The scattering of light by the sample
The conversion of fluorescence to heat
Explanation - Photobleaching occurs when fluorophores permanently lose their ability to emit light.
Correct answer is: The loss of fluorescence due to prolonged exposure to light
Q.87 In a digital image analysis workflow, what is the purpose of 'segmentation'?
To increase image brightness
To identify and separate distinct objects within an image
To convert color images to grayscale
To filter out noise
Explanation - Segmentation partitions an image into regions representing individual cells or structures.
Correct answer is: To identify and separate distinct objects within an image
Q.88 Which of the following is NOT a requirement for a successful live‑cell fluorescence experiment?
Appropriate temperature control
High‑quality objective lens
Proper buffer composition
High‑vacuum chamber
Explanation - Live‑cell imaging is performed at atmospheric pressure; vacuum is required only for EM.
Correct answer is: High‑vacuum chamber
Q.89 What does the term 'magnification' refer to in microscopy?
The size of the objective lens
The ratio of the image size to the object size
The number of pixels in the detector
The depth of field
Explanation - Magnification describes how many times larger the image appears compared to the actual sample.
Correct answer is: The ratio of the image size to the object size
Q.90 Which of the following techniques uses a laser to generate a focused beam for scanning a specimen?
Laser scanning confocal microscopy
Wide‑field fluorescence microscopy
Transmission electron microscopy
Bright‑field microscopy
Explanation - Laser scanning confocal uses a focused laser beam to scan the sample point‑by‑point.
Correct answer is: Laser scanning confocal microscopy
Q.91 Which of the following is a key advantage of using a 'super‑resolution' technique like STED over conventional confocal microscopy?
Lower phototoxicity
Higher speed of acquisition
Higher spatial resolution below the diffraction limit
Simpler experimental setup
Explanation - STED surpasses the diffraction limit by de‑exciting peripheral fluorophores.
Correct answer is: Higher spatial resolution below the diffraction limit
Q.92 In an optical system, what is the purpose of a 'dichroic mirror'?
To focus the excitation beam
To separate excitation and emission light paths
To enhance magnification
To polarize the emitted light
Explanation - A dichroic mirror reflects excitation wavelengths and transmits longer emission wavelengths.
Correct answer is: To separate excitation and emission light paths
Q.93 Which of the following is a common method to reduce phototoxicity in live‑cell imaging?
Using high laser power
Increasing exposure time
Using lower laser power and shorter exposure
Staining with heavy metals
Explanation - Lower illumination intensity and brief exposure minimize damage to living cells.
Correct answer is: Using lower laser power and shorter exposure
Q.94 Which of the following is a key feature of 'structured illumination microscopy' (SIM)?
It requires no special illumination patterns
It provides optical sectioning without a pinhole
It doubles the lateral resolution compared to conventional microscopy
It is only suitable for fixed samples
Explanation - SIM reconstructs super‑resolution images by projecting patterned illumination.
Correct answer is: It doubles the lateral resolution compared to conventional microscopy
Q.95 What is the primary benefit of using a 'water‑immersion' objective for live‑cell microscopy?
Higher numerical aperture due to refractive index matching
Simplified cleaning
Reduced photobleaching
Higher magnification
Explanation - Water immersion matches the sample medium, enabling higher NA and resolution.
Correct answer is: Higher numerical aperture due to refractive index matching
Q.96 Which of the following best describes the 'point spread function' (PSF) in a confocal microscope?
The spectral response of the detector
The 3‑D intensity distribution produced by a point source
The range of magnifications available
The optical path length difference
Explanation - PSF describes how a point of light is spread in the image due to diffraction.
Correct answer is: The 3‑D intensity distribution produced by a point source
Q.97 Which of the following imaging modalities can provide both morphological and chemical information in a single experiment?
Raman microscopy
Bright‑field microscopy
Phase‑contrast microscopy
Dark‑field microscopy
Explanation - Raman signals reveal chemical bonds while the optical image shows morphology.
Correct answer is: Raman microscopy