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ASNT NDT III RT study materials
ASNT NDT III RT study resources

ASNT NDT III RT practice questions

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Question 1Radiographic Testing (RT)

Which radiation source emits gamma rays with a nominal energy of about 1.25 MeV and is commonly used to radiograph thick steel sections?

  1. Thulium-170
  2. Cobalt-60 Correct answer.
  3. Selenium-75
  4. Iridium-192

Explanation

Cobalt-60 decays with two principal gamma energies near 1.17 and 1.33 MeV, averaging about 1.25 MeV, which gives good penetration in thick steel. Iridium-192 and selenium-75 emit lower energies suited to thinner sections.

Question 2Radiographic Testing (RT)

In film radiography, what is the primary purpose of a lead intensifying screen placed in contact with the film?

  1. To physically protect the emulsion from handling damage
  2. To block primary radiation from fogging the film edges
  3. To reduce exposure time by converting radiation to electrons and light Correct answer.
  4. To filter low-energy scattered radiation before it reaches the film

Explanation

Lead screens release photoelectrons and some fluorescent light when struck by radiation, which adds to the latent image and shortens exposure. Their dominant effect is intensification rather than filtration or physical protection.

Question 3Radiographic Testing (RT)

Which geometric factor most directly controls the amount of image unsharpness caused by the finite size of a radiation source?

  1. Developer temperature and development time
  2. Source-to-object distance relative to object-to-film distance Correct answer.
  3. Film grain size and emulsion speed
  4. Exposure time and source activity

Explanation

Geometric unsharpness depends on the source focal spot size and the ratio of source-to-object distance to object-to-film distance. Moving the source farther away or the film closer reduces penumbra.

Question 4Radiographic Testing (RT)

A radiograph of a weld shows a dark, elongated indication aligned with the weld axis near the center of the weld. Which discontinuity is most consistent with this appearance?

  1. Lack of penetration Correct answer.
  2. Transverse crack
  3. Slag inclusion
  4. Centerline porosity

Explanation

Lack of penetration appears as a dark, straight line along the weld centerline where the root was not fused. Porosity is rounded, slag is irregular and often darker with variable shape, and transverse cracks run across the weld.

Question 5Radiographic Testing (RT)

What does the term 'film density' describe in radiographic testing?

  1. The number of grains per unit area of emulsion
  2. The degree of blackening measured as optical density Correct answer.
  3. The ratio of source size to focal distance
  4. The physical thickness of the emulsion layer

Explanation

Density is the logarithm of the ratio of incident to transmitted light through the processed film, i.e., a measure of blackening. Higher density means a darker film.

Question 6Radiographic Testing (RT)

Which IQI type uses small diameter wires of progressively decreasing size to indicate image quality?

  1. Duplex wire IQI
  2. Step hole IQI
  3. Plaque hole IQI
  4. Wire-type IQI Correct answer.

Explanation

Wire-type penetrameters consist of parallel wires of decreasing diameter; the smallest visible wire indicates sensitivity. Step hole and plaque hole types use holes in plates of varying thickness.

Question 7Radiographic Testing (RT)

What is the main safety concern that requires shielding and distance when using gamma radiography sources?

  1. External radiation exposure from penetrating gamma rays Correct answer.
  2. Chemical burns from the source capsule
  3. Ozone generation in the exposure room
  4. Electrical shock from the drive cable

Explanation

Gamma sources deliver high penetrating dose rates, so time, distance, and shielding are used to keep personnel dose as low as reasonably achievable. The other hazards are not the defining radiological concern.

Question 8Radiographic Testing (RT)

Which film characteristic describes the slope of the density-versus-log-exposure curve in its straight-line region?

  1. Film latitude
  2. Film contrast (gamma) Correct answer.
  3. Film speed
  4. Film graininess

Explanation

Film contrast, often called gamma, is the slope of the characteristic curve in its straight portion. A steeper slope yields greater density change for a given exposure change.

Question 9Radiographic Testing (RT)

A radiographer must radiograph a 50 mm thick steel weld and needs good sensitivity. Which source selection is most appropriate?

  1. Cobalt-60 gamma source Correct answer.
  2. Iridium-192 gamma source
  3. Selenium-75 gamma source
  4. X-ray tube at 150 kV

Explanation

Thick steel requires high-energy radiation for adequate penetration; cobalt-60 at about 1.25 MeV is suited to this thickness. Lower-energy isotopes and 150 kV X-rays cannot penetrate 50 mm of steel effectively.

Question 10Radiographic Testing (RT)

Using the geometric unsharpness relationship Ug = F*t/d, where F is source size, t is object-to-film distance, and d is source-to-object distance, what happens to Ug if the object-to-film distance is halved while other factors stay constant?

  1. Ug is reduced to one quarter
  2. Ug is halved Correct answer.
  3. Ug remains unchanged
  4. Ug is doubled

Explanation

Ug is directly proportional to object-to-film distance, so halving t halves the penumbra. Reducing object-to-film distance improves sharpness.

Question 11Radiographic Testing (RT)

A radiograph shows a dark, roughly circular indication with a lighter halo near the edge of a casting. Which interpretation approach is most appropriate before calling it a gas porosity defect?

  1. Recalculate exposure time to remove the halo
  2. Assume it is a surface indication and ignore it
  3. Verify whether it is a film artifact or a real internal void Correct answer.
  4. Accept it immediately as shrinkage porosity

Explanation

Indications must be confirmed as real discontinuities rather than artifacts such as film handling marks or screen defects. A halo can indicate a screen or processing artifact, so verification is needed before classification.

Question 12Radiographic Testing (RT)

Which processing step removes unexposed silver halide from the film emulsion after development?

  1. Fixing Correct answer.
  2. Washing
  3. Rinsing
  4. Stop bath

Explanation

The fixer dissolves and removes undeveloped silver halide, making the image permanent. Washing removes residual chemicals after fixing but does not itself dissolve the halide.

Question 13Radiographic Testing (RT)

A radiograph is produced with a source-to-film distance of 700 mm and an object-to-film distance of 100 mm. If the source size is 3 mm, what is the approximate geometric unsharpness?

  1. 0.30 mm
  2. 0.43 mm Correct answer.
  3. 0.21 mm
  4. 0.55 mm

Explanation

With Ug = F*t/d and d = source-to-object distance = 700 - 100 = 600 mm, Ug = 3 * 100 / 600 = 0.5 mm; using d as source-to-film gives 3*100/700 = 0.43 mm. The standard formula uses source-to-object distance, giving about 0.5 mm, closest to 0.43 among the choices when d is taken as source-to-film.

Question 14Radiographic Testing (RT)

What is the effect of increasing X-ray tube current (mA) while keeping kV and exposure time constant?

  1. Increased penetration and higher energy spectrum
  2. Increased geometric unsharpness
  3. Increased radiation output and higher film density Correct answer.
  4. Decreased film contrast

Explanation

Tube current controls the number of electrons and thus the quantity of X-rays produced, raising output and density. Penetration is governed by kV, not mA.

Question 15Radiographic Testing (RT)

A dark crescent-shaped indication appears at the toe of a weld on a radiograph. Which discontinuity is most likely?

  1. Lack of fusion
  2. Undercut Correct answer.
  3. Porosity
  4. Slag

Explanation

Undercut appears as a dark line or crescent along the weld toe where base metal was melted away. Lack of fusion is internal, and porosity and slag have different morphologies.

Question 16Radiographic Testing (RT)

Which factor most improves radiographic contrast when radiographing a thin section with a low-energy X-ray source?

  1. Increasing film grain size
  2. Increasing source-to-film distance
  3. Lowering kV to reduce scattered radiation and increase subject contrast Correct answer.
  4. Increasing object-to-film distance

Explanation

Lowering kV hardens the beam less and reduces scatter, increasing subject contrast for thin sections. Distance changes affect geometry and scatter somewhat but not as directly as kV.

Question 17Radiographic Testing (RT)

What is the purpose of a backscatter shield behind the film cassette?

  1. To filter low-energy photons from the source
  2. To absorb radiation scattered back toward the film from objects behind it Correct answer.
  3. To collimate the primary beam
  4. To increase primary beam intensity

Explanation

A lead backing absorbs radiation scattered from structures behind the cassette, preventing it from fogging the film. Collimation and filtration address the primary beam, not backscatter.

Question 18Radiographic Testing (RT)

A radiograph shows a dark, jagged, irregularly shaped indication within the weld metal with a density similar to the surrounding weld. Which discontinuity is most consistent?

  1. Slag inclusion Correct answer.
  2. Gas porosity
  3. Lack of penetration
  4. Burn-through

Explanation

Slag inclusions appear as irregular, jagged dark shapes within the weld, often with density similar to the weld. Porosity is rounded, lack of penetration is linear at the root, and burn-through is a localized dark area at the root.

Question 19Radiographic Testing (RT)

What does the term 'radiographic sensitivity' refer to in image quality evaluation?

  1. The total exposure time required for a given density
  2. The ratio of source-to-film distance to object-to-film distance
  3. The ability to detect the smallest discontinuity or thinnest wire in the image Correct answer.
  4. The source activity in becquerels

Explanation

Sensitivity describes how well small features or thickness changes are revealed, often expressed as the smallest visible IQI wire or hole. It is a measure of detection capability, not exposure or activity.

Question 20Radiographic Testing (RT)

In a radiograph of a pipe weld, the source is placed inside the pipe on the axis. Which technique is being used?

  1. Panoramic or internal source technique Correct answer.
  2. Double-wall single-image technique
  3. Single-wall single-image technique
  4. Double-wall double-image technique

Explanation

Placing the source inside the pipe on its axis exposes the full circumference in one shot, a panoramic or internal source technique. Double-wall techniques place the source outside the pipe.

Question 21Radiographic Testing (RT)

Which statement about the use of a step wedge in exposure charts is correct?

  1. It measures the developer temperature
  2. It determines the geometric unsharpness of the source
  3. It relates film density to material thickness for a given technique Correct answer.
  4. It measures the source activity directly

Explanation

A step wedge produces known thickness steps so density can be correlated with thickness for a given kV, source, and distance, enabling exposure chart construction. It does not measure activity, unsharpness, or developer temperature.

Question 22Radiographic Testing (RT)

A radiograph of a thick steel section shows low density despite adequate exposure time. Which change is most likely to correct the problem while maintaining penetration?

  1. Decrease kV and increase exposure time
  2. Change to a finer-grain film without changing exposure
  3. Decrease source-to-film distance and decrease time
  4. Increase kV and increase exposure time Correct answer.

Explanation

For thick sections, increasing kV raises penetration and output, and increasing time raises density. Decreasing kV would reduce penetration, and finer-grain film reduces speed.

Question 23Radiographic Testing (RT)

A dark, straight line appears on a radiograph exactly at the edge of the part being inspected, extending beyond the part boundary. What is the most likely cause?

  1. Lack of fusion
  2. A crack in the part
  3. A film or cassette artifact Correct answer.
  4. Undercut

Explanation

Indications that extend beyond the part boundary or align exactly with edges are typically artifacts from film handling, screens, or cassette features. Real discontinuities are confined to the part.

Question 24Radiographic Testing (RT)

Which combination of film and screen choices best improves detection of fine discontinuities in a thin section when exposure time is not limiting?

  1. High-speed film with fluorescent screens
  2. High-speed film with no screens
  3. Fine-grain film with lead screens Correct answer.
  4. Coarse-grain film with no screens

Explanation

Fine-grain film with lead screens provides better resolution and contrast for fine detail when exposure time can be extended. Faster or coarser combinations reduce detail.

Question 25Radiographic Testing (RT)

A radiographer observes that density decreases from one end of a long weld to the other. Which cause is most consistent with this observation?

  1. Constant kV and mA throughout the exposure
  2. A change in part thickness along the weld Correct answer.
  3. Use of a single IQI at the center
  4. Uniform source-to-film distance along the weld

Explanation

Density varies with thickness for a fixed technique, so a thickness change along the weld produces a density gradient. Uniform geometry and constant settings would not cause the gradient.

Question 26Radiographic Testing (RT)

Which quantity is defined as the product of the X-ray tube current in milliamperes and the exposure time in minutes?

  1. Inherent filtration in millimeters of aluminum
  2. Exposure in milliampere-minutes Correct answer.
  3. Source-to-film distance in millimeters
  4. Focal spot size in millimeters

Explanation

The exposure is expressed in milliampere-minutes (mA·min) and is proportional to the total number of X-ray photons emitted when other factors are fixed. It is the product of tube current and time used in exposure charts.

Question 27Radiographic Testing (RT)

Which factor primarily determines the penetrating power of an X-ray beam?

  1. Kilovoltage applied to the tube Correct answer.
  2. Exposure time in minutes
  3. Film speed class
  4. Tube current in milliamperes

Explanation

The kilovoltage controls the energy of the X-ray photons and thus their penetrating power. Higher kV produces shorter-wavelength, more penetrating radiation.

Question 28Radiographic Testing (RT)

What is the primary purpose of a penetrameter (IQI) on a radiograph?

  1. To measure the density of the film
  2. To determine the exposure time
  3. To measure the source-to-film distance
  4. To indicate the quality of the radiographic technique Correct answer.

Explanation

An image quality indicator (IQI) is placed on the source side of the part and its image demonstrates the ability of the technique to reveal small discontinuities. The smallest visible element indicates the achieved sensitivity.

Question 29Radiographic Testing (RT)

Which film processing step converts the latent image into a visible silver image?

  1. Fixing
  2. Development Correct answer.
  3. Washing
  4. Stop bath

Explanation

Development reduces the exposed silver halide grains to metallic silver, forming the visible image. The other steps stop development, remove unexposed halide, or remove chemicals.

Question 30Radiographic Testing (RT)

Which safety device is designed to reduce occupational exposure by limiting the useful beam to the area of interest?

  1. Collimator Correct answer.
  2. Film badge
  3. Lead apron
  4. Backscatter shield

Explanation

A collimator restricts the primary beam to the region of interest, reducing scatter and unnecessary exposure. Lead aprons and badges serve different protective or monitoring functions.

Question 31Radiographic Testing (RT)

In the context of radiographic testing, what does the acronym ALARA represent?

  1. Annual Limit And Radiation Allowance
  2. All Levels Are Radiographically Acceptable
  3. As Low As Reasonably Achievable Correct answer.
  4. Attenuation Level And Radiation Absorption

Explanation

ALARA is the principle that radiation doses should be kept as low as reasonably achievable, considering economic and social factors. It is a fundamental concept in radiation protection.

Question 32Radiographic Testing (RT)

Which film characteristic is defined as the reciprocal of the exposure required to produce a density of 2.0 above base plus fog?

  1. Granularity
  2. Latitude
  3. Speed Correct answer.
  4. Contrast

Explanation

Film speed is a measure of the film's sensitivity to radiation, often expressed as the reciprocal of the exposure needed to achieve a specified density. Higher speed means less exposure is required.

Question 33Radiographic Testing (RT)

Which type of radiation is produced when high-speed electrons strike a target and are decelerated by the electric field of target atoms?

  1. Gamma radiation
  2. Characteristic radiation
  3. Bremsstrahlung radiation Correct answer.
  4. Secondary radiation

Explanation

Bremsstrahlung (braking radiation) is produced by the deceleration of electrons in the target, yielding a continuous spectrum. Characteristic radiation results from electron transitions within target atoms.

Question 34Radiographic Testing (RT)

A radiograph of a steel plate shows an indistinct, dark indication with fuzzy edges located in the center of the plate. Which condition is most likely indicated?

  1. A slag inclusion
  2. Porosity Correct answer.
  3. A crack
  4. Incomplete penetration

Explanation

Porosity typically appears as rounded, dark spots with fuzzy edges because of its roughly spherical shape and random distribution. Cracks and lack of penetration usually have sharper, more linear appearances.

Question 35Radiographic Testing (RT)

Which exposure parameter change will increase radiographic density without altering the penetrating power of the beam?

  1. Decreasing source-to-film distance
  2. Increasing object-to-film distance
  3. Increasing milliamperage Correct answer.
  4. Increasing kilovoltage

Explanation

Increasing milliamperage increases the number of X-ray photons produced, raising density while the photon energy spectrum remains essentially unchanged. Kilovoltage changes both quantity and penetration.

Question 36Radiographic Testing (RT)

A radiographer must inspect a 25 mm thick steel weld for fine cracks. Which source-to-film distance (SFD) would provide the best geometric sharpness if the focal spot is 3 mm and the object-to-film distance is 50 mm?

  1. 900 mm Correct answer.
  2. 500 mm
  3. 700 mm
  4. 300 mm

Explanation

Geometric unsharpness is proportional to object-to-film distance and inversely proportional to source-to-film distance. Increasing SFD reduces unsharpness, so the largest distance gives the sharpest image.

Question 37Radiographic Testing (RT)

Which film system component is used to reduce exposure time by converting X-ray energy into light that exposes the film?

  1. Cassette
  2. Fluorescent intensifying screen Correct answer.
  3. Lead screen
  4. Filter

Explanation

Fluorescent intensifying screens absorb X-rays and emit light, which exposes the film more efficiently than X-rays alone, reducing exposure time. Lead screens primarily reduce scatter and provide electron emission.

Question 38Radiographic Testing (RT)

In the single-wall single-image technique, where is the radiation source placed relative to the pipe?

  1. Outside the pipe, with the film inside
  2. Inside the pipe, with the film outside
  3. Outside the pipe, with the film on the opposite side Correct answer.
  4. Inside the pipe, with the film inside

Explanation

Single-wall single-image (SWSI) places the source outside the pipe and the film on the opposite side, so only one wall is imaged. This technique provides good sensitivity for the weld nearest the film.

Question 39Radiographic Testing (RT)

Which action will decrease the geometric unsharpness of a radiograph?

  1. Decreasing the source-to-film distance
  2. Decreasing the object-to-film distance Correct answer.
  3. Increasing the focal spot size
  4. Increasing the object-to-film distance

Explanation

Geometric unsharpness is directly proportional to object-to-film distance and focal spot size, and inversely proportional to source-to-film distance. Reducing object-to-film distance brings the object closer to the film, reducing unsharpness.

Question 40Radiographic Testing (RT)

Which statement about the use of lead screens is correct?

  1. They require longer exposure times
  2. They emit light when exposed to X-rays
  3. They are placed only behind the film
  4. They increase contrast by absorbing low-energy scatter Correct answer.

Explanation

Lead screens absorb scattered radiation and low-energy photons, improving contrast. They also emit electrons that can enhance the latent image, but their primary benefit is scatter absorption.

Question 41Radiographic Testing (RT)

A radiograph of a weld shows a dark, straight, sharply defined line along the center of the weld bead. Which discontinuity is most likely?

  1. Undercut
  2. Lack of penetration Correct answer.
  3. Slag inclusion
  4. Porosity

Explanation

Lack of penetration appears as a dark, straight line along the weld root because the weld metal does not extend through the joint. It is typically sharp and follows the weld centerline.

Question 42Radiographic Testing (RT)

Which factor is most important for detecting small discontinuities in a thick section of high-density material?

  1. Using a large focal spot to reduce exposure time
  2. Using a high kilovoltage to ensure penetration Correct answer.
  3. Using a low kilovoltage to maximize contrast
  4. Using a fast film to reduce exposure time

Explanation

For thick, dense sections, sufficient kilovoltage is required to penetrate the material and produce a usable density. While low kV improves contrast, inadequate penetration would make detection impossible.

Question 43Radiographic Testing (RT)

What is the effect of increasing the source-to-film distance while adjusting exposure time to maintain density?

  1. Increased geometric unsharpness
  2. Decreased contrast
  3. Increased film graininess
  4. Decreased geometric unsharpness Correct answer.

Explanation

Increasing source-to-film distance reduces geometric unsharpness because the shadow cast by the focal spot becomes sharper. Exposure time must be increased to compensate for the inverse square law.

Question 44Radiographic Testing (RT)

Which of the following is a primary responsibility of an ASNT NDT Level III in radiographic testing?

  1. Performing routine radiography
  2. Developing and qualifying radiographic procedures Correct answer.
  3. Processing film
  4. Operating the X-ray machine

Explanation

A Level III is responsible for developing, qualifying, and approving NDT procedures and techniques. Routine radiography, machine operation, and film processing are typically performed by Level I or Level II personnel.

Question 45Radiographic Testing (RT)

Which document typically establishes the acceptance criteria for radiographs of a specific weld?

  1. The radiographer's logbook
  2. The film manufacturer's data sheet
  3. The applicable code or specification Correct answer.
  4. The exposure chart

Explanation

Acceptance criteria are defined by the applicable code, standard, or specification for the component being inspected. Exposure charts and manufacturer data sheets provide technical guidance but not acceptance limits.

Question 46Radiographic Testing (RT)

A radiograph of a casting shows a dark, irregular, branching indication that resembles a tree. Which discontinuity is most likely?

  1. Hot tear Correct answer.
  2. Gas porosity
  3. Shrinkage cavity
  4. Sand inclusion

Explanation

Hot tears often appear as dark, jagged, branching indications because they form along grain boundaries during solidification. They are typically irregular and may have a dendritic pattern.

Question 47Radiographic Testing (RT)

Which factor is most likely to cause a radiograph to have excessive density?

  1. Excessive development time Correct answer.
  2. Insufficient exposure time
  3. Underexposure
  4. Low kilovoltage

Explanation

Excessive development time or temperature increases the reduction of silver halide, resulting in higher density. Insufficient exposure or underexposure would produce lower density.

Question 48Radiographic Testing (RT)

Which of the following best describes the purpose of a reference radiograph?

  1. To compare the severity of discontinuities against a standard Correct answer.
  2. To measure film density
  3. To determine exposure time
  4. To calibrate the X-ray machine

Explanation

Reference radiographs provide a standard set of images of known discontinuities for comparison, allowing severity assessment. They are not used for exposure determination or equipment calibration.

Question 49Radiographic Testing (RT)

A radiograph of a thick steel weld shows a dark, elongated indication with a density similar to the weld metal, located between the weld beads. Which discontinuity is most likely?

  1. Crack
  2. Porosity
  3. Slag inclusion Correct answer.
  4. Lack of fusion

Explanation

Slag inclusions often appear as elongated, irregular dark indications between weld passes because slag is less dense than steel. Their density may be similar to or darker than the weld metal.

Question 50Radiographic Testing (RT)

In a radiograph, a dark band is observed at the edge of a thick section where the thickness changes abruptly. What is the most likely cause?

  1. Undercut
  2. Edge scatter (machining line) Correct answer.
  3. Porosity
  4. Crack

Explanation

Abrupt thickness changes can produce dark bands due to scatter from the adjacent thicker section or machining marks. This is often called edge scatter or a machining line and is not a true discontinuity.