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ASNT VT Level III study materials
ASNT VT Level III study resources

ASNT VT Level III practice questions

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Question 1Visual Testing Method Fundamentals and Theory

Which property of the human eye most directly limits the smallest defect a visual test can reliably detect?

  1. Color adaptation time
  2. Peripheral motion sensitivity
  3. Angular resolution (visual acuity) Correct answer.
  4. Pupil diameter under dim light

Explanation

Detection of a small indication depends on the angle it subtends at the eye, so visual acuity sets the practical limit on resolvable detail at a given viewing distance. The other properties affect comfort, lighting needs, or motion detection rather than the minimum resolvable size.

Question 2Visual Testing Method Fundamentals and Theory

A surface must be inspected at a viewing distance of 600 mm. Using the common rule that the eye resolves about 0.1 mm at 250 mm, what is the approximate smallest resolvable detail at 600 mm?

  1. 0.04 mm
  2. 1.20 mm
  3. 0.24 mm Correct answer.
  4. 0.60 mm

Explanation

Resolution scales linearly with viewing distance, so the resolvable detail is 0.1 mm multiplied by 600/250, about 0.24 mm. This scaling is the basis for specifying maximum viewing distance in procedures.

Question 3Visual Testing Method Fundamentals and Theory

In visual testing, the term 'contrast' refers to which relationship?

  1. The distance from the eye to the test surface
  2. The ratio of reflected light from the indication to that from its background Correct answer.
  3. The angle between the light source and the test surface
  4. The time the inspector spends scanning each area

Explanation

Contrast is the luminance difference between an indication and its surroundings, expressed as a ratio or percentage. Adequate contrast is required for an indication to be seen at all.

Question 4Visual Testing Method Fundamentals and Theory

An inspector views a dark crack on a light, diffusely reflecting surface. Which lighting change would most improve the visibility of this indication?

  1. Increasing the angle of incidence to near grazing Correct answer.
  2. Reducing the overall illuminance on the part
  3. Using a broad diffuse source directly above the part
  4. Moving the light farther away without changing angle

Explanation

Grazing or near-grazing light rakes across surface-breaking discontinuities, casting shadows and increasing the luminance difference between crack and background. Direct diffuse lighting tends to wash out such fine indications.

Question 5Visual Testing Method Fundamentals and Theory

Which statement correctly describes the relationship between illumination and the ability to detect low-contrast indications?

  1. Detection improves with illuminance up to a point, after which glare can degrade performance Correct answer.
  2. Detection always improves as illuminance increases without limit
  3. Illumination has no effect once the eye is dark-adapted
  4. Only the color temperature of the source matters for detection

Explanation

Adequate illuminance raises contrast above the eye's threshold, but excessive or poorly directed light produces glare that reduces effective contrast and causes fatigue. Procedures therefore specify minimum illuminance and control glare.

Question 6Visual Testing Method Fundamentals and Theory

What is the primary purpose of a reference standard or comparator in visual testing?

  1. To measure the surface roughness numerically
  2. To verify the inspector's visual acuity record
  3. To calibrate the light meter before each shift
  4. To provide a known appearance against which indications are judged acceptable or rejectable Correct answer.

Explanation

Reference standards present known discontinuities or surface conditions so the inspector can compare observed indications against an acceptance criterion. They reduce subjectivity in accept/reject decisions.

Question 7Visual Testing Method Fundamentals and Theory

Which optical aid is most appropriate for inspecting a surface that is physically inaccessible to direct viewing but visible along a line of sight?

  1. A black light
  2. A borescope Correct answer.
  3. A photometer
  4. A magnifying loupe

Explanation

A borescope or fiberscope relays an image along a line of sight into cavities and restricted areas. Loupes magnify but still require direct access to the surface.

Question 8Visual Testing Method Fundamentals and Theory

Why do visual testing procedures specify a maximum viewing distance rather than only a magnification?

  1. Distance controls the surface roughness perceived
  2. Resolvable detail depends on the angle subtended at the eye, which distance controls Correct answer.
  3. Magnification is irrelevant to visual testing
  4. Viewing distance determines the wavelength of light used

Explanation

Because acuity is angular, the same magnification at a greater distance subtends a smaller angle and reveals less detail. Specifying distance ensures the required detail actually falls within resolving capability.

Question 9Visual Testing Method Fundamentals and Theory

Which condition describes 'veiling glare' as it affects visual inspection?

  1. A loss of resolution caused by an unclean lens
  2. A shadow cast by the part onto the background
  3. Stray light scattered within the optical system or eye that reduces image contrast Correct answer.
  4. A color shift caused by the light source spectrum

Explanation

Veiling glare is non-image-forming light that raises the luminance of the background and lowers contrast. It commonly arises from bright sources near the line of sight or reflective surroundings.

Question 10Visual Testing Method Fundamentals and Theory

Which surface preparation requirement is common to most visual testing techniques before inspection?

  1. The surface must be clean and free of contaminants that could mask discontinuities Correct answer.
  2. The surface must be roughened to increase contrast
  3. The surface must be cooled below ambient temperature
  4. The surface must be painted to a uniform color

Explanation

Contaminants such as oil, scale, or dirt can hide or mimic discontinuities, so cleaning is a prerequisite for meaningful visual inspection. Surface finish requirements are then specified by the applicable procedure.

Question 11Visual Testing Method Fundamentals and Theory

An inspector must detect a 0.5 mm wide crack on a large flat plate. Which combination best supports reliable detection?

  1. Diffuse overhead light plus a distant viewing position
  2. Reduced illuminance plus a colored filter
  3. Grazing light at a shallow angle plus a viewing distance within the procedure limit Correct answer.
  4. Direct on-axis light plus a wide scanning angle

Explanation

Small surface cracks are best revealed by raking light that produces shadow contrast, while adequate resolution requires the viewing distance to remain within the specified limit. Both conditions must be satisfied together.

Question 12Visual Testing Method Fundamentals and Theory

Which statement about the eye's adaptation to brightness is correct for visual inspection?

  1. The eye adapts instantly with no loss of detection capability
  2. Adaptation only affects color perception, not contrast
  3. Adaptation is irrelevant when a light meter reads adequate illuminance
  4. Sudden changes in illuminance temporarily reduce sensitivity, so inspectors should allow adaptation time Correct answer.

Explanation

The eye requires time to adjust when moving between bright and dim areas, and during that period detection sensitivity is reduced. Procedures and good practice allow adaptation time and avoid abrupt lighting changes.

Question 13Visual Testing Method Fundamentals and Theory

What does the term 'resolution' mean in the context of a visual testing imaging system?

  1. The color accuracy of the display
  2. The total field of view covered by the camera
  3. The brightness of the image produced
  4. The smallest separation between two features that can still be distinguished as separate Correct answer.

Explanation

Resolution is the ability to distinguish closely spaced features as distinct rather than merged. It is distinct from field of view, brightness, and color fidelity.

Question 14Visual Testing Method Fundamentals and Theory

A remote visual inspection camera has a fixed sensor. To improve the resolved detail on a target, the inspector should:

  1. Reduce the illumination on the target
  2. Increase the display brightness only
  3. Decrease the distance to the target or increase optical magnification Correct answer.
  4. Increase the field of view to capture more area

Explanation

Resolved detail improves when the target subtends more sensor elements, achieved by moving closer or increasing optical magnification. Widening the field of view spreads the same sensor over more area and reduces detail.

Question 15Visual Testing Method Fundamentals and Theory

Which factor most strongly determines whether a given indication will be perceived during a visual scan?

  1. The ambient humidity in the inspection area
  2. The luminance contrast and size of the indication relative to the background Correct answer.
  3. The part's manufacturing date
  4. The color of the inspector's clothing

Explanation

Perception depends on the indication producing a sufficient contrast signal over a sufficient angular size. Environmental or administrative factors do not determine detectability.

Question 16Visual Testing Method Fundamentals and Theory

An inspector observes an indication whose appearance changes markedly as the viewing angle is altered. This behavior most likely indicates:

  1. An internal void open to the surface
  2. A surface feature such as a scratch or gouge rather than a volumetric internal discontinuity Correct answer.
  3. A subsurface lamination
  4. A material composition error

Explanation

Surface-breaking features show strong angle-dependent appearance because their visibility depends on shadowing and reflection geometry. Internal features not open to the surface are generally not visible at all by direct visual means.

Question 17Visual Testing Method Fundamentals and Theory

Which statement best describes the role of magnification in visual testing?

  1. It always improves detection regardless of lighting
  2. It eliminates the effect of viewing distance
  3. It improves detection of small indications only when resolution and lighting are adequate Correct answer.
  4. It replaces the need for surface cleaning

Explanation

Magnification increases the angular size of detail but cannot create contrast or resolution that the optical system and lighting do not provide. Adequate illumination and a clean surface remain prerequisites.

Question 18Visual Testing Method Fundamentals and Theory

Which of the following is a correct statement about the use of color in visual testing?

  1. Only monochromatic light should be used
  2. Color has no effect on visual detection
  3. Color differences can aid detection but may also create false indications from surface staining Correct answer.
  4. Color vision deficiencies are irrelevant to inspection

Explanation

Color contrast can help distinguish an indication from its background, but stains, oxidation, or coatings can mimic discontinuities. Inspectors should also have verified color vision.

Question 19Visual Testing Method Fundamentals and Theory

When a procedure specifies a minimum illuminance at the test surface, the measurement should be taken:

  1. At the light source output aperture
  2. At the ceiling of the inspection area
  3. At the inspector's eye position facing the source
  4. At the surface, with the meter oriented to receive light as the surface does Correct answer.

Explanation

Illuminance requirements apply to the light reaching the surface being inspected, so the meter is placed at the surface and oriented to match the surface's receiving geometry. Measuring elsewhere gives a value not representative of inspection conditions.

Question 20Visual Testing Method Fundamentals and Theory

Which of the following best explains why inspectors scan a surface systematically rather than randomly?

  1. Systematic scanning reduces the chance that an area is missed and improves consistency Correct answer.
  2. Random scanning is faster and equally reliable
  3. Systematic scanning increases illumination on the part
  4. Random scanning improves contrast

Explanation

A defined scanning pattern ensures full coverage and repeatable results, reducing the likelihood that an indication is overlooked. Scanning method does not change illumination or contrast.

Question 21Visual Testing Method Fundamentals and Theory

An inspector using a magnifier notes that the image appears distorted near the edges of the field. This is most likely caused by:

  1. Incorrect light source color temperature
  2. Lens aberrations inherent to the optical design Correct answer.
  3. Insufficient surface illumination
  4. Improper surface cleaning

Explanation

Optical aberrations such as field curvature and distortion cause image degradation away from the center of the field. Lighting, cleaning, and color temperature do not produce geometric distortion.

Question 22Visual Testing Method Fundamentals and Theory

Which statement about the relationship between surface finish and visual detection is correct?

  1. Rough surfaces always improve detection of fine cracks
  2. Surface finish does not affect visual detection
  3. A smoother surface always makes indications harder to see
  4. A rough surface scatters light and can reduce the contrast of small indications Correct answer.

Explanation

Rough surfaces scatter light in many directions, lowering the luminance contrast that makes small indications visible. Surface finish is therefore considered when establishing inspection conditions.

Question 23Visual Testing Method Fundamentals and Theory

What is the primary function of a light source's spectral output in visual testing?

  1. It controls the inspector's adaptation time
  2. It determines the viewing distance limit
  3. It sets the surface roughness criterion
  4. It influences the color contrast and appearance of indications relative to the background Correct answer.

Explanation

The spectrum of the source affects how colors render and how an indication contrasts with its surroundings. It does not set geometric or surface criteria.

Question 24Visual Testing Method Fundamentals and Theory

Which of the following conditions would most likely produce a false indication during visual inspection?

  1. A machining mark that resembles a crack Correct answer.
  2. A confirmed porosity pit
  3. A verified surface-breaking crack
  4. A documented weld undercut

Explanation

False indications arise from surface conditions that mimic discontinuities, such as tool marks, scratches, or stains. The other listed items are actual discontinuities rather than mimics.

Question 25Visual Testing Method Fundamentals and Theory

An inspector must compare two indications of different sizes under identical lighting. Which factor is most important to ensure a valid comparison?

  1. Using a different light source for each indication
  2. Changing the scan pattern between observations
  3. Viewing the larger indication from farther away
  4. Keeping viewing distance, angle, and illumination the same for both Correct answer.

Explanation

A valid comparison requires controlled conditions so that observed differences reflect the indications rather than the viewing setup. Distance, angle, and illumination all affect apparent size and contrast.

Question 26Visual Testing Method Fundamentals and Theory

What is the primary purpose of a reference standard in visual testing?

  1. To verify the inspector's visual acuity
  2. To provide a known comparison for evaluating indications Correct answer.
  3. To measure the illumination level at the test surface
  4. To calibrate the magnification of optical aids

Explanation

A reference standard or comparator is used to establish a known condition against which indications can be compared. It helps the inspector judge acceptability by direct visual comparison. The other options describe different functions not primarily associated with reference standards.

Question 27Visual Testing Method Fundamentals and Theory

Which optical aid is most appropriate for inspecting a surface that is physically inaccessible to direct viewing but visible from a distance?

  1. A telescope Correct answer.
  2. A mirror
  3. A magnifying glass
  4. A borescope

Explanation

A telescope is designed to magnify distant objects, making it suitable for viewing surfaces that are far away but not directly accessible. A borescope is used for internal or confined spaces, a mirror for changing the line of sight, and a magnifying glass for close-up inspection.

Question 28Visual Testing Method Fundamentals and Theory

Which property of a light source most directly determines the amount of light energy falling on a test surface per unit area?

  1. Luminance of the surface
  2. Luminous intensity of the source
  3. Color temperature of the source
  4. Illuminance at the surface Correct answer.

Explanation

Illuminance is defined as the luminous flux incident per unit area on a surface and is expressed in lux or foot-candles. It directly quantifies the light energy per unit area reaching the surface, independent of the source's directional characteristics.

Question 29Visual Testing Method Fundamentals and Theory

According to standard visual testing practice, what is the recommended minimum illuminance at the inspection surface for general visual examination?

  1. 100 lux (10 fc)
  2. 500 lux (50 fc)
  3. 1000 lux (100 fc) Correct answer.
  4. 2000 lux (200 fc)

Explanation

General visual examination typically requires a minimum of 1000 lux (about 100 foot-candles) at the surface to ensure reliable detection of surface indications. Lower levels are acceptable only for less critical examinations or when specified by procedure.

Question 30Visual Testing Method Fundamentals and Theory

What is the typical minimum near-distance visual acuity required for an inspector performing visual testing?

  1. 20/40 (6/12) with or without correction
  2. 20/20 (6/6) with or without correction Correct answer.
  3. 20/30 (6/9) with or without correction
  4. 20/25 (6/7.5) with or without correction

Explanation

Most visual testing standards require the inspector to demonstrate near-distance acuity of at least 20/20 (6/6) in at least one eye, with or without corrective lenses. This ensures the inspector can resolve fine details at the specified viewing distance.

Question 31Visual Testing Method Fundamentals and Theory

Which statement correctly describes the relationship between viewing distance and the minimum resolvable detail for a given eye?

  1. Minimum resolvable detail is independent of viewing distance.
  2. Minimum resolvable detail increases proportionally with viewing distance. Correct answer.
  3. Minimum resolvable detail decreases as viewing distance increases.
  4. Minimum resolvable detail is determined solely by the illumination level.

Explanation

The eye's angular resolution is roughly constant, so the linear size of the smallest resolvable detail increases in direct proportion to the viewing distance. This is why procedures often specify a maximum viewing distance to ensure adequate resolution.

Question 32Visual Testing Method Fundamentals and Theory

When selecting a magnifier for visual inspection, which combination best ensures that the magnifier will reveal finer detail than the unaided eye?

  1. A magnifier with high magnification and a large lens diameter
  2. A magnifier with the shortest possible focal length regardless of optical quality
  3. A magnifier with the largest available lens diameter regardless of magnification
  4. A magnifier with magnification sufficient to resolve the required detail and with low aberration Correct answer.

Explanation

The magnifier must provide enough magnification to make the target detail subtend a resolvable angle, and its optical quality must be high enough to avoid distortion or blur that would mask the detail. Lens diameter and focal length affect working distance and field of view but are secondary to adequate magnification and aberration control.

Question 33Visual Testing Method Fundamentals and Theory

What is the primary reason for using a borescope or fiberscope in visual testing?

  1. To measure the depth of surface discontinuities
  2. To provide illumination for photographic documentation
  3. To view areas that are physically inaccessible for direct line-of-sight inspection Correct answer.
  4. To magnify small surface indications beyond the eye's capability

Explanation

Borescopes and fiberscopes are remote visual inspection tools designed to allow viewing of internal or otherwise inaccessible areas without disassembly. They may include magnification and illumination, but their primary purpose is access.

Question 34Visual Testing Method Fundamentals and Theory

An inspector is examining a rough, dark surface for small cracks. Which lighting technique is most likely to improve contrast and detection?

  1. Diffuse, uniform illumination from directly above
  2. High-angle, diffuse illumination from a large area source
  3. Backlighting through the part
  4. Low-angle, directional illumination Correct answer.

Explanation

Low-angle directional lighting creates shadows and highlights that enhance surface relief and discontinuities such as cracks, especially on rough or dark surfaces. Diffuse or high-angle lighting tends to wash out such features.

Question 35Visual Testing Method Fundamentals and Theory

Which statement best describes the effect of contrast on visual detection of an indication?

  1. Detection improves as the contrast between the indication and its background increases. Correct answer.
  2. Contrast has no effect on detection if illumination is sufficient.
  3. Contrast affects only the color perception of the indication, not its detection.
  4. Detection improves as the contrast between the indication and its background decreases.

Explanation

Visual detection depends on the difference in luminance or color between the indication and its surroundings. Greater contrast makes the indication more distinguishable from the background, improving the likelihood of detection.

Question 36Visual Testing Method Fundamentals and Theory

An inspector observes a surface indication that appears as a straight, sharp line under one lighting angle but becomes indistinct at another angle. What does this behavior most likely indicate?

  1. A false indication caused by a scratch or mark on the surface
  2. A true surface-breaking discontinuity such as a crack Correct answer.
  3. A subsurface discontinuity that is not visible
  4. A change in surface color due to lighting

Explanation

True cracks often show strong directional dependence because their faces reflect light differently as the viewing or lighting angle changes, causing the indication to appear and disappear. False indications from surface marks tend to remain visible regardless of angle.

Question 37Visual Testing Method Fundamentals and Theory

What is the primary purpose of a resolution test target (such as a line-pair gauge) in visual testing?

  1. To determine the magnification of a lens
  2. To verify the ability of an imaging system to resolve fine detail Correct answer.
  3. To calibrate the color accuracy of a camera
  4. To measure the illuminance at the test surface

Explanation

A resolution test target contains patterns of lines or dots of known spacing and is used to evaluate the spatial resolution capability of an imaging system, including the eye, camera, or borescope. It provides an objective measure of how small a detail can be distinguished.

Question 38Visual Testing Method Fundamentals and Theory

Which of the following best explains why the human eye may fail to detect a small indication during a visual scan even when it is within the field of view?

  1. The indication falls outside the eye's sharp-focus area and is not noticed. Correct answer.
  2. The indication is located in the foveal region of the retina.
  3. The inspector is using a magnifier with too high a magnification.
  4. The illumination level is above the recommended maximum.

Explanation

Only the fovea provides sharp vision; objects outside this small central area are perceived with lower acuity and may be missed unless the eye scans across them. Systematic scanning ensures that all areas pass through the fovea.

Question 39Visual Testing Method Fundamentals and Theory

When using a borescope with a fixed light source, which factor most affects the ability to see fine surface detail in a dark cavity?

  1. The diameter of the borescope
  2. The intensity and direction of illumination at the target Correct answer.
  3. The length of the borescope insertion tube
  4. The color of the borescope's outer sheath

Explanation

In a dark cavity, the amount and angle of light reaching the target determine whether sufficient contrast is available to resolve detail. Inadequate or misdirected illumination is a common cause of missed indications in remote visual inspection.

Question 40Visual Testing Method Fundamentals and Theory

Which statement correctly describes the relationship between surface condition and the visibility of a surface discontinuity under visual testing?

  1. A smooth, clean surface generally provides better contrast for detecting fine indications than a rough, contaminated surface. Correct answer.
  2. Surface condition has no effect on the visibility of indications if illumination is adequate.
  3. A painted surface always enhances the detection of cracks by providing a uniform background.
  4. A rough surface always improves the visibility of small cracks by creating shadows.

Explanation

A smooth, clean surface reduces scattering and provides a more uniform background, making it easier to see contrast differences caused by indications. Roughness and contamination can mask fine details and create false indications.

Question 41Visual Testing Equipment and Materials

Which property of a light source most directly determines how much fine surface detail a visual inspection can resolve?

  1. Color temperature
  2. Wavelength Correct answer.
  3. Beam angle
  4. Luminous efficacy

Explanation

Resolution in visual testing is limited by wavelength because diffraction sets the smallest detail that can be distinguished; shorter wavelengths allow finer detail to be seen. Color temperature, beam angle, and efficacy affect appearance, coverage, and brightness but do not set the fundamental resolution limit.

Question 42Visual Testing Equipment and Materials

What is the primary purpose of a magnifier in visual testing?

  1. To increase the contrast of indications
  2. To extend the working distance to the part
  3. To increase the apparent size of indications Correct answer.
  4. To filter out ultraviolet radiation

Explanation

A magnifier increases the angular size of the image on the retina, making small indications easier to see. It does not by itself improve contrast, filter radiation, or serve primarily to extend working distance.

Question 43Visual Testing Equipment and Materials

Which instrument provides a direct numerical measure of surface roughness for correlation with visual comparators?

  1. Profilometer Correct answer.
  2. Photometer
  3. Borescope
  4. Gaussmeter

Explanation

A profilometer measures surface profile numerically, typically as Ra or similar parameters, and can be used to correlate visual comparator standards. Borescopes are for internal viewing, photometers measure light, and gaussmeters measure magnetic fields.

Question 44Visual Testing Equipment and Materials

Which type of light source is preferred when a broad, uniform, shadow-free illumination of a large surface is required?

  1. A focused spot lamp
  2. A black light
  3. A monochromatic laser
  4. A diffuse area light Correct answer.

Explanation

A diffuse area light spreads illumination evenly over a wide area and minimizes shadows, which is desirable for general surface examination. Spot lamps create shadows, lasers produce narrow beams, and black lights are for fluorescent indications.

Question 45Visual Testing Equipment and Materials

What does the resolution of a borescope or videoscope primarily depend on?

  1. The number of imaging elements or pixels Correct answer.
  2. The length of the insertion tube
  3. The stiffness of the articulation
  4. The diameter of the light guide

Explanation

Image resolution is set by how many discrete picture elements or fibers sample the image; more elements yield finer detail. Tube length, articulation stiffness, and light guide diameter affect access and illumination but not the fundamental image sampling.

Question 46Visual Testing Equipment and Materials

What is the function of a reticle in a visual testing optical instrument?

  1. To polarize the incoming light
  2. To protect the lens from contamination
  3. To provide a reference scale for measuring features Correct answer.
  4. To increase the field of view

Explanation

A reticle is a graduated scale placed in the optical path so that the size of an observed feature can be measured against known divisions. It does not polarize light, protect the lens, or widen the field of view.

Question 47Visual Testing Equipment and Materials

Why must a light meter used for visual testing be calibrated?

  1. To allow the meter to measure temperature
  2. To ensure the readings trace to a known reference standard Correct answer.
  3. To reduce the battery consumption of the meter
  4. To widen the spectral response of the sensor

Explanation

Calibration establishes traceability so that illuminance or luminance readings are accurate and comparable to specified acceptance values. It does not change the meter's spectral response, power use, or measurement quantity.

Question 48Visual Testing Equipment and Materials

Which accessory is used to view surfaces inside a small-diameter tube where direct line of sight is impossible?

  1. A surface comparator
  2. A magnifying glass
  3. A weld gauge
  4. A borescope Correct answer.

Explanation

A borescope relays an image around bends or through long small-diameter openings, allowing internal surfaces to be viewed. Magnifiers, comparators, and weld gauges require direct access to the surface.

Question 49Visual Testing Equipment and Materials

A technician needs to detect very fine surface-breaking cracks on a smooth machined part. Which lighting approach best enhances these indications?

  1. Backlighting through the part
  2. A directional light at a low angle to the surface Correct answer.
  3. Diffuse floodlighting at a shallow angle
  4. High-angle diffuse illumination

Explanation

Low-angle directional light casts shadows in surface-breaking cracks and discontinuities, making them visible where diffuse light would wash them out. Backlighting is for through-transmission, and high-angle diffuse light reduces shadow contrast.

Question 50Visual Testing Equipment and Materials

When selecting a magnifier for a specified inspection, the required magnification and the field of view must be balanced. What happens to the field of view as magnification increases for a given instrument?

  1. The field of view becomes independent of working distance
  2. The field of view stays constant
  3. The field of view increases
  4. The field of view decreases Correct answer.

Explanation

Higher magnification narrows the area visible at once, so the field of view decreases. This trade-off requires scanning more area or choosing magnification appropriate to the feature size.