cargar 100 a 200 Flashcards by TOM GM

98 A term used to define the timing relationships involved in alternating current signals is:

(A) Magnitude.
(B) phase.
(C) impedance.
(D) reactance.
(E) time-gain correction.

(B) phase.

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99 The impedance of a test coil can be represented by the vector sum of:

(A) inductive reactance and resistance.
(B) capacitive reactance and resistance.
(C) inductive reactance and capacitive reactance.
(D) inductive reactance, capacitive reactance, and resistance.

(A) inductive reactance and resistance.

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100 Disadvantages of using a surface probe coil for the eddy current inspection of small-diameter tubing include:

(A) inability to detect small discontinuities.
(B) slow inherent speed.
(C) inherent mechanical problems.
(D) all of the above.
(E) both b and c.

(E) both b and c.

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101 The term “fill factors” applies to:

(A) a surface coil.
(B) coaxial cable.
(C) an encircling coil.
(D) the ability to null an eddy current instrument.

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102 Which of the following materials would be more likely used as a mounting material for a probe coil?

(A) Aluminum.
(B) Plastic.
(C) Copper.
(D) Nonferromagnetic steel.

(B) Plastic.

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103 Which of the following is not a commonly used eddy current testing read-out mechanism?

(A) Signal generator.
(B) Meter.
(C) Cathode ray tube.
(D) Strip-chart recorder.

(A) Signal generator.

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104 Reference standards used for eddy current testing:

(A) must contain artificial discontinuities such as notches and drilled holes.
(B) must contain natural discontinuities such as cracks and inclusions.
(C) must be free of measurable discontinuities but may contain artificial or natural discontinuities or may be free of discontinuities, depending on the test system and the type of test being conducted.
(D) are not typically described in any of the above.

(D) are not typically described in any of the above.

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105 Which of the following conditions is not important when selecting specimens to be used as reference standards?

(A) The specimen should be of the same size and shape as the piece to be tested.
(B) The specimen should be of the same materials and have the same heat treatment as the piece to be tested.
(C) The surface finish of the specimen should be the same as the piece to be tested.
(D) If the material is aluminum, the surface should be anodized.
(E) All of the above conditions are important.

(D) If the material is aluminum, the surface should be anodized.

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106 Which of the following conditions would be the most difficult to detect when eddy current testing a rod using an encircling coil?

(A) A short surface crack that has a depth of 10% of the rod diameter.
(B) A small inclusion in the center of the rod.
(C) A 5% change in diameter.
(D) A 10% change in conductivity.

(B) A small inclusion in the center of the rod.

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107 The thickness of nonconductive coatings on a conductive base can be most simply measured by:

(A) observing the lift-off effect caused by the coating.
(B) testing both sides of the specimen.
(C) varying the test frequency over a given range during the test.
(D) using a specially shaped encircling coil.

(A) observing the lift-off effect caused by the coating.

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108 Some of the products com monly tested using encircling coils are:

(A) rods, tubes, and wire.
(B) interior of hollow tubes.
(C) sheets and metaled foil.
(D) all of the above.

(A) rods, tubes, and wire.

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109 It is often posible to sort various alloys of a nonmagnetic metal by means of an eddy current test when:

(A) there is a unique range of permeability values for each alloy.
(B) there is a unique range of conductivity values for each alloy.
(C) the direction of induced eddy currents varies for each alloy.
(D) the magnetic domains for each alloy are different.
(E) the alloy is slightly magnetic; but not if totally nonmagnetic.

(B) there is a unique range of conductivity values for each alloy.

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110 When eddy current testing tubing with a system that includes a frequency discriminating circuit, which of the following variables would be classified as a high-frequency variable?

(A) Small discontinuities.
(B) Conductivity changes.
(C) Diameter changes.
(D) Wall thickness variations.

(A) Small discontinuities.

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111 Which of the following is not a candidate for testing by the eddy current method?

(A) A 102 mm (4 in.) thick plate to be tested for discontinuities throughout the plate.
(B) Tubing to be tested for surface cracks.
(C) Rod to be tested for laps and seams.
(D) Tubing to be tested for variation in outside diameter.
(E) Both a and d.

(A) A 102 mm (4 in.) thick plate to be tested for discontinuities throughout the plate.

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112 Thermal resistance is:

(A) analogous to electrical current.
(B) a material’s impedance to heat flow.
(C) proportional to the fourth power of emissivity.
(D) proportional to the rate of heat flow.

(B) a material’s impedance to heat flow.

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113 Conductive heat transfer cannot take place:

(A) across a vacuum.
(B) within organic materials such as wood.
(C) between two solid materials in contact.
(D) between dissimilar metals.

(A) across a vacuum.

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114 The radiation of infrared thermal energy from a target surface:

(A) occurs most efficiently in a vacuum.
(B) is proportional to the fourth power of the absolute surface temperature.
(C) is directly proportional to surface emissivity.
(D) does all of the above.

(D) does all of the above.

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115 Thermal radiation reaching the surface of an object can be:

(A) absorbed only in the presence of atmosphere.
(B) reflected and absorbed only in a vacuum.
(C) absorbed, reflected, and transmitted.
(D) transmitted only if the surface is organic.

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116 The following spectral band is included in the infrared spectrum:

(A) 0.1-5.5 µm.
(B) 0.3-10.6 µm.
(C) 0.4-20.0 µm.
(D) 0.75-100 µm.

(D) 0.75-100 µm.

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117 As a surface cools, the peak of its radiated infrared energy:

(A) shifts to longer wavelengths.
(B) shifts to shorter wavelengths.
(C) remains constant if emissivity remains constant.
(D) remains constant even if emissivity varies.

(A) shifts to longer wavelengths.

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118 A graybody surface with an emissivity of 0.04 would be:

(A) transparent to infrared radiation.
(B) a fairly good emitter.
(C) almost a perfect reflector.
(D) almost a perfect emitter.

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119 If a surface has an emissivity of 0.35 and a reflectivity of 0.45, its transmissivity would be:

(A) impossible to determine without additional information.
(B) 0.80.
(C) 0.10
(D) 0.20.

(D) 0.20.

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The spectral band in which glass transmits infrared radiation most efficiently is the:

(A) 3.0-6.0 µm region.
B) 2.0-3.0 µm region.
(C) 6.0-9.0 µm region.
(D) 9.0-1 1.0 µm region.

(B) 2.0-3.0 µm region.

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121 Infrared thermal detectors:

(A) have a broad, flat spectral response.
(B) have much faster response times than photon detectors.
(C) usually require cooling to operate properly.
(D) have much greater sensitivity than photon detectors.

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122 A diffuse reflecting surface is: (A) a polished surface that reflects incoming energy at a complementary angle. (B) a surface that scatters reflected energy in many directions. (C) also called a specular reflecting surface. (D) usually transparent to infrared radiation.

(B) a surface that scatters reflected energy in many directions.

123 The thermal resolution of an instrument is the same as: (A) the temperature accuracy. (B) minimum resolvable temperature difference. (C) temperature repeatability. (D) the minimum spot size.

(B) minimum resolvable temperature difference.

124 The instantaneous spot size of an instrument is related to the (A) instantaneous field of view and the working distance. (B) thermal resolution. (C) spectral band width and the working distance. (D) speed of response and the working distance.

(A) instantaneous field of view and the working distance.

125 The thermal resolution of an instrument tends to: (A) improve as the target temperature increases. (B) degrade as the target temperature increases. (C) remain constant regardless of the target temperature. (D) improve with increasing working distance.

(A) improve as the target temperature increases.

126 The 3-5 µm spectral region is well suited for operation of instruments: (A) measuring sub-zero temperature targets. (B) measuring targets at extremely long working distances. (C) measuring targets warmer than 200 °C (392 °F) (D) operating at elevated ambient temperatures.

127 Adding an infrared spectral filter to an instrument limits the spectral band: (A) to only wavelengths longer than a specified wavelength. (B) to only wavelengths shorter than a specified wavelength. (C) to only wavelengths between two specified wavelengths. (D) all of the above are true.

(B) to only wavelengths shorter than a specified wavelength.

128 A line scanner can be best used to produce a thermogram of a sheet process when: (A) the sheet process is moving at a uniform rate. (B) emissivity is known. (C) the process material is a non-graybody. (D) the sheet process is hotter than 200 °C (392 °F) .

(A) the sheet process is moving at a uniform rate.

129 Most infrared focal plane array imagers: (A) use more costly optics than scanning radiometers. (B) offer better spatial resolution than scanning radiometers. (C) offer better thermal resolution than scanning radiometers. (D) offer more diagnostics features than scanning radiometers.

(B) offer better spatial resolution than scanning radiometers.

130 When measuring the temperature of a non-gray target: (A) the viewing angle is not critical. (B) always assume an emissivity of 1.0 (C) reflections off the near surface may be ignored. (D) errors may be caused by hot sources in the background.

(D) errors may be caused by hot sources in the background.

131 Unfinished metal surfaces usually have: (A) high and uniform emissivities. (B) low and uniform emissivities. (C) non-graybody characteristics. (D) low specular reflectivity.

(B) low and uniform emissivities.

132 Thermal diffusivity is: (A) high for metals and low for porous materials. (B) the same for all metals. (C) low for metals and high for porous materials. (D) the same for all porous materials.

(A) high for metals and low for porous materials.

133 The 3-dimensional resistance to temperature change within a material is called: (A) diffuse reflectivity. (B) thermal effusivity. (C) thermal conductance. (D) spectral transmittance.

(B) thermal effusivity.

134 Which of the following systems or components are candidates for leak testing? (A) Piping and pressure vessels. (B) Refrigeration piping. (C) Vacuum chambers. (D) All of the above. (E) Both a and b.

(D) All of the above.

135 A helium mass spectrometer is used in which of the following NDT method(s) ? (A) X-ray spectroscopy. (B) Optical holography. (C) Acoustic holography. (D) Leak testing. (E) Both b and c.

(D) Leak testing.

136 Which of the following is a technique of leak testing? (A) Bubble detection. (B) Measurement of pressure changes. (C) Halogen "sniffing." (D) All of the above.

(D) All of the above.

137 Potentially, the most sensitive leak testing techniq ue is the: (A) bubble test. (B) pressure change test. (C) mass spectrometer test. (D) Iiquid penetrant test.

138 Establishing differential pressure between the test object and environment is an essential element in which of the following NDT methods? (A) X-ray diffraction. (B) Neutron radiography. (C) Leak testing. (D) Gamma radiography. (E) Eddy current testing.

139 Which of the following best describes the type of leak test used when the interior of the test object is evacuated and a tracer gas is applied to the exterior, while the leak detector is connected to the evacuating system? (A) Static leak test. (B) Helium leak test. (C) Dynamic leak test. (D) Halogen leak test. (E) Sniffer leak test.

140 Assuming no significant leakage, if the temperature increased during a pressure drop leak test, the pressure in the system under test would: (A) increase. (B) remain the same. (C) decrease. (D) first increase, then decrease to its former level.

(A) increase.

141 If the sensitivity of the halogen leak detector is maintained constant throughout a test, which of the following is true upon completion of the test? (A) No leaks of a certain size or larger have gone undetected. (B) The total leak rate of the test object is less than a certain amount. (C) The instrument and test procedure were capable of detecting leakage of a certain size during the test. (D) All of the above.

142 All leak detection methods are dependent upon: (A) barometric pressure. (B) gas or fluid flow. (C) mass spectrometers analysis. (D) mean free paths of helium flow.

(B) gas or fluid flow.

143 In an evacuated system, sensitivity of a pressure change leak test is dependent not only on the pressure change observed, but also on the degree of outgassing. Outgassing is best defined as: (A) the viscosity of the pressurizing gas. (B) being directly proportional to the temperature of the gas. (C) the release of gases which were absorbed into the walls of the test container. (D) the drop in test pressure due to leakage from the vacuum manifold. (E) a phenomenon whereby gases in an evacuated system eventually leak to the outside of the system if vacuum is maintained.

144 The tendency of a liquid penetrant to enter a discontinuity is primarily related to: (A) the viscosity of the penetrant. (B) capillary forces.( C) the chemical inertness of the penetrant. (D) the specific gravity of the penetrant. (E) all of the above.

(B) capillary forces.

145 Liquid penetrant testing is a nondestructive test that can be used for: (A) locating and evaluating all types of discontinuities in a test specimen. (B) locating and determining the length, width, and depth of discontinuities in a test specimen. (C) determining the tensile strength of a test specimen. (D) locating discontinuities open to the surface. (E) a, b, and d.

(D) locating discontinuities open to the surface.

146 Which of the following is not a characteristic that applies to liquid penetrant testing? (A) This method can accurately measure the depth of a crack or discontinuity. (B) This method can be used for on-site testing of large parts. (C) This method can be used to find shallow surface discontinuities. (D) This method can be made more or less sensitive by using different penetrant materials.

(A) This method can accurately measure the depth of a crack or discontinuity.

147 The property of a dye used in penetrant materials to emit light of a range of wavelengths different from the wavelength of light that excites the emission is called: (A) emissivity. (B) irradiation. (C) black light. (D) spectrum blocking. (E) fluorescence.

(E) fluorescence.

148 When using a fluorescent, post-emulsifier penetrant, the length of time the emulsifier is allowed to remain on the part is critical for detecting shallow discontinuities. The optimum length of time should be: (A) 10 seconds. (B) 5 seconds. (C) 2-3 minutes. (D) determined by experimentation.

(D) determined by experimentation.

149 A red penetrant indication against white background is most likely to be seen when: (A) dry developers are used. (B) visible dye penetrants are used. (C) fluorescent post-emulsified penetrants are used. (D) wet developers are used. (E) ultraviolet light is used with visible dye penetrants.

(B) visible dye penetrants are used.

150 The most widely accepted method for removing excessive water-washable penetrant from the surface of a test specimen is by: (A) using a wet rag. (B) using a water spray rinse. (C) washing the part directly under water running from a tap. (D) immersing the part in water.

(B) using a water spray rinse.

151 Which of the following penetrant systems is generally considered the least sensitive? (A) Water-washable; visible dye. (B) Solvent-removable; visible dye. (C) Water-washable; fluorescent dye. (D) Post-emulsified; visible dye.

(A) Water-washable; visible dye.

152 When performing a liquid penetrant test using solvent-removable visible dye penetrant, there are several ways to remove excess penetrant from the surface of the part. Which of the methods listed below is generally regarded as most suitable for giving accurate test results? (A) Squirting solvent over the surface with no more than 10 psi pressure. (B) Wiping with a solvent-soaked cloth, then wiping with a dry cloth. (C) Wiping with a solvent-dampened cloth, then wiping with dry cloths. (D) wiping ·with dry wipes, then wiping with a solvent-dampened cloth, and finally wiping with dry cloth.

(D) wiping ·with dry wipes, then wiping with a solvent-dampened cloth, and finally wiping with dry cloth.

153 A problem with retesting a specimen that has been previously tested using liquid penetrant is that: (A) the penetrant may form beads on the surface. (B) the penetrant residue left in discontinuities may not readily dissolve and the retest may be misleading. (C) the penetrant will lose a great deal of its color brilliance. (D) none of the above are correct statements.

(B) the penetrant residue left in discontinuities may not readily dissolve and the retest may be misleading.

154 A commonly used method of checking the overall performance of a penetrant material system is to: (A) determine the viscosity of the penetrant. (B) measure the wet ability of the penetrant. (C) compare two sections of artificially cracked specimens. (D) do all of the above.

155 The function of emulsifier in the post-emulsified penetrant process is to: (A) more rapidly drive the penetrant into deep, tight cracks. (B) react with the surface penetrant to make the penetrant water-washable. (C) add fluorescent dye or pigment to the penetrant. (D) provide a coating to which dry powder developer can adhere. (E) emulsify surface oils and greases to facilitate their removal.

(B) react with the surface penetrant to make the penetrant water-washable.

156 Which of the following statements does not apply to developers used during penetrant testing? (A) Developers are normally highly fluorescent. (B) Some developers furnish a contrasting background during inspection. (C) Developers absorb or blot the penetrant that remains in discontinuities after the excess penetrant has been removed. (D) All of the above are true statements.

(A) Developers are normally highly fluorescent.

157 The penetrant indication for a cold shut on the surface of a casting will normally be: (A) a dotted line. (B) a cluster of small indications. (C) a smooth continuous line. (D) a large bulbous indication. (E) undetectable since cold shuts are closed over on the surface.

158 A crack-type discontinuity will generally appear as: (A) a rounded indication. (B) a continuous line, either straight or jagged. (C) a broad, fuzzy indication. (D) random round or elongated holes.

(B) a continuous line, either straight or jagged.

159 In a penetrant test, scattered round indications on the surface of a part could be indicative of: (A) fatigue cracks. (B) porosity. (C) weld laps. (D) hot tears. (E) grinding cracks.

(B) porosity.

160 Which of the following are typical nonrelevant indications found in penetrant testing? (A) Indications due to part geometry or part design configurations. (B) Nonmagnetic indications. (C) Multiple indications. (D) Nonlinear indications. (E) Indications on low-stressed areas of the part.

(A) Indications due to part geometry or part design configurations.

161 Which of the statements below best states the results of sandblasting for cleaning surfaces to be penetrant tested? (A) Discontinuities may be closed. (B) Oil contaminants might be sealed in the discontinuities. (C) The sand used in the sandblasting operation may be forced into the discontinuity. (D) The sandblasting operation may introduce discontinuities into the part. (E) None of the above.

(A) Discontinuities may be closed.

162 The penetrant indication of a forging lap will normally be: (A) a round or nearly round indication. (B) a cluster of indications. (C) a thin continuous line. (D) a dotted line.

163 Aluminum alloy test specimens that have been tested by the liquid penetrant method should be thoroughly cleaned after testing because: (A) acid in the penetrant may cause severe corrosion. (B) the alkalines in wet developers and most emulsifiers could cause surface pitting, particularly in moist atmospheres. (C) the oily residue from the test will severely inhibit the application of paint on aluminum alloys. (D) a chemical reaction between the penetrant and aluminum could cause a fire.

(B) the alkalines in wet developers and most emulsifiers could cause surface pitting, particularly in moist atmospheres.

164 Penetrants may be used for leak detection: (A) if surfaces are clean. (B) if both sides are accessible. (C) in dilute form during hydro-test. (D) effectively by using fluorescent tracers. (E) in all of the above.

(E) in all of the above.

165 Which of the following is a discontinuity that might be found in rolled bar stock? (A) Blow holes. (B) Shrinkage laps. (C) Cracks or seams. (D) Insufficient penetration.

166 Anodized surfaces are usually considered poor candidates for high sensitivity liquid penetrant examination because the anodizing process produces a conversión layer that: (A) is extremely smooth and slick. (B) has a multitude of extremely small pores. (C) may have alkaline residue which "quenches" the penetrant. (D) cannot be cleaned by ordinary processes. (E) flakes off on contact with penetrant materials.

(B) has a multitude of extremely small pores.

167 Which of the following penetrant methods does not normally require a source of electricity to properly cond uct a test? (A) Water-washable fluorescent penetrant method. (B) Post-emulsified fluorescent penetrant method. (C) Visible dye penetrant method. (D) None of the above require a source of electricity.

168 Which of the following statements is true concerning penetrant testing of welds with rough surfaces? (A) The post-emulsified process offers advantages over the water-washable process. (B) Weld surfaces must be ground flush in order to expose all subsurface discontinuities. (C) if the solvent-removal process is used, the best developer would be an aqueous suspension. (D) Welds with rough surfaces cannot be successfully tested by any penetrant method. (E) None of the above statements is true.

(E) None of the above statements is true.

169 Which of the following materials cannot be tested by magnetic particle techniques? (A) High alloy steels. (B) Tool steels. (C) Copper alloys. (D) Ferritic stainless steels. (E) Both c and d.

170 Materials that are strongly attracted to a magnet are called: (A) magnetized. (B) nonmagnetic. (C) ferromagnetic. (D) magnetic.

171 Magnetic lines of force (magnetic fields) are oriented in what direction in relation to the direction of the magnetizing current? (A) Parallel. (B) At right angles. (C) At a 45° angle. (D) One angular orientation is random.

(B) At right angles.

172 Magnetizing flux is a term that relates to: (A) describing the direction of current flow in an electromagnet. (B) the manner by which magnetism flows through space. (C) the number of lines of force associated with a magnetic field. (D) permanent magnets only.

173 Subjecting a part to a magnetic field that is constantly reversing in polarity and gradually diminishing in strength accomplishes which of the following? (A) The part is magnetized. (B) The part is demagnetized. (C) The remanence of the magnetic field is increased. (D) Deep-iying discontinuities are more easily located.

(B) The part is demagnetized.

174 Circular magnetization is useful in the detection of: (A) circumferential cracks. (B) longitudinal cracks. (C) cracks in cylindrical parts at right angles to the long axis of the part. (D) Both a and c.

(B) longitudinal cracks.

175 In which magnetizing method is the current passed directly through the part, thereby setting up a magnetic field at right angles to the current flow? (A) Longitudinal magnetization. (B) Coil magnetization. (C) Central conductor magnetization. (D) All of the above. (E) None of the above.

(E) None of the above.

176 Which of the following is a major disadvantage of using the prod method? (A) The magnetic field may be applied in the wrong direction. (B) The inspection surface may be arc burned. (C) Magnetic saturation may occur. (D) The operator's eyes may be burned by arc strikes.

(B) The inspection surface may be arc burned.

177 Inspecting a part by applying the magnetic particle suspension while the current is flowing is called the: (A) continuous method. (B) dry method. (C) residual method. (D) demagnetization method.

(A) continuous method.

178 How is the inside diameter of a cylinder best magnetized? (A) By a head shot. (B) By using prods at either end. (C) With a central conductor placed between contact heads. (D) With the cylinder placed crosswise in a solenoid.

179 The amount of amperage used for magnetic particle inspection using the prod method is based on the: (A) thickness of the part. (B) distance between the prods. (C) diameter of the prods. (D) total length of the part. (E) all of the above.

(B) distance between the prods.

180 Demagnetization of a part is usually not necessary if the part is: (A) small. (B) inspected with the continuous method. (C) to be hardened by heat treatment after inspection. (D) high carbon steel to be welded after inspection.

181 Which of the following is an advantage of the dry method over the wet method? (A) It is more sensitive for detecting fine surface cracks. (B) It is more capable of providing full surface coverage on irregularly shaped parts. (C) It is easier to use for field inspection with portable equipment. (D) It is faster when testing a number of small parts. (E) The equipment cost is lower.

182 Fluorescent magnetic particles are used in preference to visible magnetic particles: (A) when parts are big and bulky. (B) to take advantage of the fluorescent lights that are normally used in plants. (C) if parts are for railroad applications. (D) to increase the speed and reliability of detecting very small discontinuities.

(D) to increase the speed and reliabi lity of detecting very small discontinuities.

183 The most versatile type of magnetic particle equipment is: (A) portable equipment. (B) the stationary horizontal machine. (C) the mobile power unit. (D) the automatic machine. (E) a field kit.

(B) the stationary horizontal machine.

184 Magnetic particle inspection methods are recognized as superior to liquid penetrant techniques when the: (A) surfaces of the test object are corroded. (B) surface is anodized. (C) parts are painted. (D) part is made from austenitic steel.

185 When using direct current, an indication is detected. What is the next logical step to determine if the indication results from a surface or subsurface condition? (A) Reinspect using the surge method. (B) Demagnetize and apply powder. (C) Reinspect at higher amperage. (D) Reinspect using alternating current.

186 A requirement to use magnetic particle testing on a part should also include: (A) a fabrication and service manual. (B) a statement on the drawing that requires a magnetic particle test. (C) the procedure to be used and acceptance criteria. (D) the method of test and service conditions.

187 The statement that magnetic particle testing can be applied to plated and painted parts: (A) is true regardless of the thickness of the coating. (B) may be true if flux densities are increased to compensate for the coating thickness. (C) is true only for circular magnetism. (D) is not true under any circumstances.

(B) may be true if flux densities are increased to compensate for the coating thickness.

188 The best type of magnetizing current for inspection of fatigue cracks is: (A) direct current. (B) alternating current. (C) half-wave direct current. (D) full-wave rectified direct current. (E) any of the above if the current is correct.

(B) alternating current.

189 A star-shaped indication was seen on the cover pass of a weld. What type of discontinuity was indicated? (A) A cooling crack. (B) A crater crack. (C) A slag inclusión. (D) A lack of fusion. (E) An arc burn.

(B) A crater crack.

190 For maximum sensitivity in magnetic particle inspection of rough welds: (A) the weld should be wire brushed to remove slag and scale. (B) standard test weldments should be used for comparison. (C) the weld bead should be coated with lacquer. (D) the weld bead should be ground flush with the plate surfaces.

(D) the weld bead should be ground flush with the plate surfaces.

191 The highest intensity sources of thermal neutrons are: (A) Cf-252 isotopes (B) accelerators (C) nuclear reactors (D) none of the above

(A) Cf-252 isotopes

192 Neutrons for fast-neutron radiography are obtainable from: (A) accelerators. (B) radioactive sources. (C) reactors. (D) all of the above. (E) none of the above.

(D) all of the above.

193 A radioactive source used for neutron radiography is: (A) Pu-239. (B) Co-60. (C) Cs-137. (D) Cf-252. (E) all of the above.

(D) Cf-252.

194 The energy of the neutron is expressed in which of the following units of measurement? (A) Curies. (B) Roentgens. (C) Half-life. (D) Electron-volts. (E) REMs.

(D) Electron-volts.

195 A normally desirable feature of a thermal neutron beam for neutron radiography is: (A) low gamma radiation intensity. (B) relatively low fast-neutron intensity (C) low angular divergence. (D) both a and b.

196 Material that slows down neutrons is called: (A) a moderator. (B) an accumulator. (C) a limitor. (D) a reducer. (E) a collimator.

(A) a moderator.

197 The primary radiation mechanism for darkening X-ray film when the direct neutron radiography process is used with gadolinium screens is: (A) alpha particles. (B) electrons. (C) gamma rays. (D) light emission.

(B) electrons.

198 Neutron radiography using the transfer method requires that the imaging screen: (A) be placed behind the film. (B) be placed in front of the film. (C) be very thin. (D) become radioactive. (E) emit light.

(D) become radioactive.

199 Which of the following neutron radiography converter foils cannot be used for transfer or indirect radiography? (A) Dysprosium. (B) Indium. (C) Gadolinium. (D) Gold.

200 The most suitable films for producing neutron radiographs are: (A) red sensitive films. (B) instant-type films. (C) industrial X-ray films. (D) medical X-ray films. (E) emulsions that contain no silver halides.

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