ASNT Ultrasonic Testing - Level III Practice Questions — 10 Free (2026)

An eddy current procedure on a given alloy produces a standard depth of penetration of 0.5 mm at 100 kHz. If the Level III revises the technique to operate at 25 kHz on the same material, the new standard depth of penetration is approximately:

• A. 0.25 mm
• B. 0.5 mm
• C. 0.71 mm
• D. 1.0 mm ✓
• E. 2.0 mm

For a fixed material, standard depth of penetration varies inversely with the square root of frequency. Cutting the frequency to one quarter therefore doubles the penetration depth. ASNT Level III Study Guide Basic, Section 2 - Electromagnetic Testing

A 20 mm crystal works at a wavelength of 3.0 mm. What is the near field length?

• A. 17 mm
• B. 25 mm
• C. 33 mm ✓
• D. 48 mm
• E. 67 mm

The extent grows with the square of the crystal size, which is why a large probe chosen for penetration costs the region nearest the surface. ISO 16810 general principles of ultrasonic testing

In classifying iron-carbon alloys for a materials course, the Level III notes that alloys are considered cast irons rather than steels when the carbon content exceeds approximately:

• A. 0.4 percent
• B. 0.8 percent
• C. 2.0 percent ✓
• D. 4.3 percent
• E. 6.7 percent

Roughly 2 percent carbon marks the practical upper boundary of the steel range; above it the alloy solidifies with eutectic carbon phases and is classed as cast iron. ASNT Level III Study Guide Basic, Chapter 5 - Ferrous Metals

An angle beam weld examination is performed with a refracted 60 degree shear wave in steel. Compared with the longitudinal velocity in the same steel, the velocity of the shear wave used is:

• A. roughly twice the longitudinal velocity
• B. roughly half the longitudinal velocity ✓
• C. about ten percent lower than the longitudinal velocity
• D. about one quarter of the longitudinal velocity
• E. exactly the same

In steel the shear velocity is on the order of 3.2 km per second versus about 5.9 km per second for longitudinal waves, roughly a one to two ratio. This velocity difference is fundamental to angle beam calibration and distance calculations. ASNT Level III Study Guide Basic, Section 2 - Ultrasonic Testing

A gamma radiography source produces a dose rate of 400 mR per hour at 2 m. With no added shielding, what dose rate should the radiation safety plan predict at 8 m from the source?

• A. 6.25 mR per hour
• B. 25 mR per hour ✓
• C. 50 mR per hour
• D. 100 mR per hour
• E. 200 mR per hour

Dose rate from a point source varies inversely with the square of distance. Quadrupling the distance from 2 m to 8 m reduces the rate by a factor of sixteen. ASNT Level III Study Guide Basic, Section 2 - Radiographic Testing

A specification requires finding and quantifying an extremely small leak in a sealed stainless steel vessel. Which leak testing technique offers the greatest sensitivity?

• A. ultrasonic listening for escaping gas
• B. bubble immersion testing
• C. helium mass spectrometer testing ✓
• D. ammonia sensitized paper testing
• E. pressure change (pressure decay) measurement over time

Mass spectrometer techniques using helium tracer gas detect far smaller leakage rates than bubble, pressure change, chemical, or sonic techniques. They also provide a quantitative leak rate rather than a simple indication. ASNT Level III Study Guide Basic, Section 2 - Leak Testing

Radiographic testing produces a usable flaw image primarily because:

• A. flaws fluoresce when struck by penetrating radiation
• B. the film emulsion is chemically sensitive to the specific alloy being radiographed and darkens accordingly
• C. scattered radiation concentrates around discontinuities
• D. radiation reflects from internal flaw surfaces
• E. different part thicknesses and densities absorb different amounts of radiation ✓

Radiography works on differential absorption: a void or low-density region attenuates less radiation than the surrounding metal, so more radiation reaches the detector and produces a darker image area. Reflection and fluorescence of the flaw play no role in image formation. ASNT Level III Study Guide Basic, Section 2 - Radiographic Testing

In pulse-echo ultrasonic testing, a discontinuity is detected because it:

• A. absorbs all of the transmitted sound
• B. changes the electrical conductivity of the part
• C. emits its own acoustic signal when insonified
• D. converts the sound beam into heat that the instrument measures as a loss
• E. reflects part of the sound beam back to the transducer ✓

A discontinuity presents an acoustic impedance mismatch, so a portion of the incident sound energy is reflected and returns to the same transducer, where its arrival time indicates reflector depth. The method relies on reflection, not absorption or emission by the flaw. ASNT Level III Study Guide Basic, Section 2 - Ultrasonic Testing

Within an SNT-TC-1A program, which individual is expected to be capable of training and examining NDT Level I and Level II personnel for certification in the methods in which that individual is certified?

• A. the NDT Level III ✓
• B. the NDT Instructor
• C. any NDT Level II
• D. the certifying authority's designee
• E. an outside agency representative

Among the defined capabilities of the highest qualification level is training and examining subordinate personnel for certification in the methods held. This duty is written into the level description itself rather than assigned to instructors or outside parties. ASNT Level III Study Guide Basic, Section 1 - SNT-TC-1A Paragraph 4.3.3

During an internal audit of a written practice prepared under SNT-TC-1A, which finding should the auditing Level III flag as inconsistent with the recommended practice?

• A. The written practice was issued without review and approval by the employer's NDT Level III. ✓
• B. The written practice records departures from SNT-TC-1A recommendations together with their technical justification.
• C. The written practice assigns each certification level its responsibility for determining acceptability of materials to the applicable codes.
• D. The written practice sets out, for each certification level, what training is owed, what experience counts, and what examinations must be passed.
• E. The written practice is kept on file and made available for customer review.

Section 5 expects the document to be reviewed and approved by the employer's Level III, maintained on file, and to describe per-level requirements and responsibilities. Skipping the Level III review step therefore conflicts with the recommended practice, while the other findings match it. ASNT Level III Study Guide Basic, Chapter 2 - Recommended Practice No. SNT-TC-1A