A

Thermal & Infrared Testing Method

Questions & Answers Book

Q
Supplement to
Recommended Practice No. SNT-TC-1A
Book J

& Levels I, II and III

Review Questions

The American Society for

Nondestructive
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to BassamInc.
AbdElFattah AbdelAzeem. The American Society for
Catalog No.: 2025
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ASNT grants non-exclusive, non-transferable license of this material to Bassam AbdElFattah AbdelAzeem. ASNT grants non-exclusive, non-transferable license of this material to Bassam AbdElFattah AbdelAzeem.
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 A
Thermal & Infrared Testing Method
Questions & Answers Book

Q
Supplement to
Recommended Practice No. SNT-TC-1A

&
Book J

Levels I, II and III

Review Questions

The American Society for

Nondestructive Testing, Inc.
ASNT grants non-exclusive, non-transferable license of this material to Bassam AbdElFattah AbdelAzeem.
All rights reserved. © ASNT 2024. To report unauthorized use, contact: customersupport@asnt.org
IR_Q&A_10_13_reprint Q8:Q&A Sample 2 10/14/13 3:28 PM Page ii

ii

Published by
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ISBN-13: 978-1-57117-197-9 (print)

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 iii

Contents

Acknowledgments iv

Recommended References v

Reference Usage vi

Level I Questions 1

Level II Questions 7

Level III Questions 15

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 iv

Acknowledgments

Thank you to Terry Clausing, Drysdale & Associates, Inc., and Rob Spring, Snell Group, for
writing and coordinating this edition of Supplement to Recommended Practice SNT-TC-1A
(Q & A Book) Infrared and Thermal Testing Method.

Thank you also to the following contributors who assisted with the peer review of this book:

Doug Burleigh Alberto F. Reyna

Patrick L. Cerny Bob Rogers
Jacky C.H. Chen Dave Ronzani
Babu S.K. Daniel R. Ryan
Grace Liang Dan Simon
Kathryn M. Lee Kris Krumreich Simmons
Bernie Lyon Jeffrey G. Thompson
Scott Miller Raymond HO Fook Wing
Gary Orlove Werner Yzelman
Philip Raw John Zabita
K. Ravindran

Cynthia M. Leeman
Educational Materials Supervisor

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 v

Recommended References
Thermal and Infrared Testing Method
The following references were used in formulating the questions contained in this book.

References
A. Maldague, X.P.V., tech. ed., Patrick O. Moore, ed. Nondestructive Testing Handbook, third edition: Volume 3,
Infrared and Thermal Testing. Columbus, OH: The American Society for Nondestructive Testing, Inc. 2001.
B. Incropera, F.P., and David P. Dewitt. Fundamentals of Heat and Mass Transfer, 5th Edition. Hoboken, NJ: John
Wiley & Sons. 2001.
C. Guyer, E.C. Handbook of Applied Thermal Design. Philadelphia, PA: Taylor & Francis. 1999.
D. Holman, J.P. Experimental Methods for Engineers. Boston, MA. McGraw-Hill. 2001.
E. Holst, G.C. Testing and Evaluation of Infrared Imaging Systems. Maitland, FL. JCD Pub. Co. 1993.
F. Kaplan, H. ASNT LIII Study Guide: Infrared and Thermal Testing Method. Columbus, OH. The American Society
for Nondestructive Testing, Inc. 2001.
G. ASTM C 1060, “Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities
of Frame Buildings.” Annual Book of ASTM Standards. West Conshohocken, PA; American Society for Testing and
Materials. Most recent edition.
H. ASTM E 1153, “Standard Test Method for Efficacy of Sanitizers Recommended for Inanimate Non-Food Contact
Surfaces.” Annual Book of ASTM Standards. West Conshohocken, PA; American Society for Testing and
Materials. Most recent edition.
I. ASTM E 2582, “Standard Practice for Infrared Flash Thermography of Composite Panels and Repair Patches
Used in Aerospace Applications.” Annual Book of ASTM Standards. West Conshohocken, PA; American Society
for Testing and Materials. Most recent edition.
J. Recommended Practice No. SNT-TC-1A: Personnel Qualification and Certification in Nondestructive Testing.
Columbus, OH. The American Society for Nondestructive Testing, Inc. Most recent edition.
Each question found in this book contains letter(s) and page number(s) in bold type immediately following the
answers. For example,

5. The first law of thermodynamics states:

a. energy moving into a body equals the energy leaving a body if it is at steady state
b. energy moves from areas of high temperature to areas of low temperature
c. energy moves from cooler areas to warmer areas
d. energy moving out of a body equals the energy transmitting through the body.
B.13

In this example, the letter “B” refers to Reference B in the list provided above and 13 is the specific page in the
reference where the answer to the question can be found.

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 vi

Reference Usage

Reference A: Total =114 Reference F: Total = 1

Level I 27 Level I 0
Level II 40 Level II 0
Level III 47 Level III 1

Reference B: Total = 10 Reference G: Total = 3

Level I 2 Level I 0
Level II 4 Level II 3
Level III 4 Level III 0

Reference C: Total = 15 Reference H: Total = 3

Level I 12 Level I 1
Level II 2 Level II 2
Level III 1 Level III 0

Reference D: Total = 8 Reference I: Total = 6

Level I 5 Level I 0
Level II 2 Level II 0
Level III 1 Level III 6

Reference E: Total = 4
Level I 2
Level II 1
Level III 1

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 Level I Questions: Thermal & Infrared Testing Method 1

Level I Questions
Thermal and Infrared Testing Method

1. One calorie is equivalent to how much 4. The second law of thermodynamics

heat energy? states:

a. raising the temperature of 1 lb of a. energy moving into a body equals the

water 1 °F energy leaving a body if it is at steady
b. raising the temperature of 1 g of water state
1 °C b. energy moves from areas of high
c. raising the temperature of 1 lb of temperature to areas of low
water 1 °C temperature
d. raising the temperature of 1g of water c. energy moves from cooler areas to
1 °F warmer areas
A.26 d. energy moving out of a body equals
the energy transmitting through the
2. Which of the following is incorrect? body
D.355
a. 0 °C = 32 °F
b. -40 °C = -40 °F 5. The first law of thermodynamics states:
c. °C = 32 + (9/5 × °F)
d. 100 °C = 212 °F a. when energy moving into a body plus
A.27 any internal energy generated equals
the energy leaving a body, that body is
3. Newton’s Law of convective cooling states in a steady state condition
that: b. energy moves from areas of high
temperature to areas of low
a. the rate of heat loss is proportional to temperature
the heat capacity of the body and its c. energy moves from cooler areas to
surface area warmer areas
b. the rate of cooling is inversely d. energy moving out of a body equals
proportional to the temperature the energy transmitting through the
c. the rate of heat loss is inversely body.
proportional to the temperature of the B.13
body
d. the rate of heat loss of a body is 6. Which of the following temperature
proportional to the difference in scales is considered an absolute scale?
temperature between the body and its
fluid surroundings. a. Fahrenheit
A.54 b. Boltzmann
c. Celsius
d. kelvin
D.356

6d 5a 4b 3d 2c 1b Answer key:

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 2 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

7. Which of the following temperature 13. You are inspecting an energized 440 V
scales is considered to be a relative scale? electrical three-phase fused disconnect.
The fuse caps on the fuses are copper and
a. Rankine appear cooler than the fuse cardboard
b. Boltzmann bodies. What is probably the reason?
c. Celsius
d. kelvin a. the fuse caps are emitting the coolness
D.356 inside themselves
b. the fuse caps are radiating less energy
8. For every degree on the Celsius and reflecting the cooler room
temperature scale how many degrees are temperatures
on the Fahrenheit scale? c. the fuse bodies are actually warmer
than the fuse caps
a. 5/9 - 32 d. the fuse bodies are reflecting your
b. 1.8 body’s warmth
c. 32 A.36
d. 100
D.356 14. Emittance of a surface may vary with
which of the following?
9. The material property that relates to the
rate that heat flows though a solid a. thermal conductance
material is called: b. angle of view
c. thermal resistance
a. thermal conductivity d. coefficient of convective heat transfer
b. convective efficiency A.298
c. conductive efficiency
d. emissive conductivity 15. A low sloped roof is inspected in the early
B.4 evening after a sunny day. Wet absorbent
roof insulation appears warmer than the
10. A micron is a unit of: dry insulation because:

a. length a. the wet insulation is a better emitter of

b. wave amplitude thermal radiation
c. temperature b. the wet insulation is more reflective
d. roughness than the dry insulation
A.33 c. the dry insulation cools off slower
than the wet insulation
11. A micron is a unit of measure that is: d. the wet insulation cools off slower
than the dry insulation
a. one thousandth of a meter A.57
b. one thousand thousandth of a inch
c. one millionth of a meter 16. Which of the following equations is used
d. one millionth of an inch to calculate the amount of radiant energy
A.33 emitted from a surface?

12. Which material below is transmissive to a. R+A+T=1

long wave (8-14 μm) infrared radiation? b. Q = σe T4
c. µm = b/T absolute
a. polyethylene film d. E = mc2
b. glass A.38; D.9
c. rubber
d. human skin
A.292

16b 15d 14b 13b 12a 11c 10a 9a 8b 7c

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 Level I Questions: Thermal & Infrared Testing Method 3

17. Which of the following IR camera 22. Thermal infrared radiation occurs at
settings may affect a radiometric wavelengths:
temperature measurement?
a. shorter than X-rays
a. span b. shorter than visible light
b. level c. longer than visible light
c. palette d. longer than radio waves
d. focus A.33; C.12-59,
C.12-61
23. An opaque graybody surface with an
18. Which of the following camera emissivity of 0.04 would be:
parameters is not adjustable in
post-processing computer software? a. transparent to infrared radiation
b. a fairly good emitter
a. span c. almost a perfect reflector
b. level d. almost a perfect emitter
c. emissivity A.94; C.12-63
d. range
C.12-61 24. The radiant energy emitted by an object
is a function of what power of its absolute
19. A thick ceramic coffee mug has an temperature?
emissivity of 0.84 in the 8-14 μm wave
band. What is its reflectivity? a. first power
b. second power
a. 0.84 c. third power
b. 0.48 d. fourth power
c. 0.34 A.89
d. 0.16
C.12-64 25. What are the three modes of heat
transfer?
20. The temperature of an aluminum bus bar
is being measured. You have determined a. reflected, transmitted, emitted
emissivity is 0.15. What is the reflectivity b. conductive, convective, radiative
of the bus bar? c. absorption, emission, transmission
d. temperature, thermal movement,
a. 0.0 absorbency
b. 0.15 A.54
c. 0.85
d. 1.0 26. A quick and simple technique for
A.94; C.12-63 improving the emissivity of highly
reflective surfaces is to:
21. A perfect thermal mirror would have an
emittance equal to: a. use a shorter wavelength infrared
camera
a. 0.0 b. apply black electrical tape to the
b. 0.01 surface
c. 0.5 c. cover the surface with aluminum foil
d. 1.0 d. adhere black thin film polyethelene
A.94; C.12-63 A.30; C.12-64

26b 25b 24d 23c 22c 21a 20c 19d 18d 17d

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 4 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

27. What can we say for certain about a clear 31. What does IFOV stand for?
piece of thin plastic?
a. increasing field of view
a. it is transparent to infrared b. instantaneous field of view
b. it is opaque to infrared c. infringing field of view
c. its emissivity is less than 1 d. image field of view
d. its reflectivity is more than 1 A.281
A.89; C.12-62
32. At what temperature does the emittance
28. A large variance of the viewing angle of thermal radiation begin?
from the normal (90°) to a non-metallic
surface of interest ________ the emitted a. above -273 K
energy sensed. b. at 0 °C
c. above 0 K
a. decreases d. above -460 R
b. increases linearly A.27
c. increases exponentially
d. has no effect on 33. Why do a block of wood and a piece of
A.95 steel at the same temperature feel so
different when they come into contact
29. In an infrared roof moisture survey, what with your body?
effects cause the areas of roof over wet
insulation to be warmer at night than a. the thermal conductivity of the steel is
those over dry insulation? greater
b. the thermal conductivity of the wood
a. high heat capacity of water and is greater
daytime insolation c. the wood is a much better emitter
b. increase thermal resistance of wet than the steel
insulation d. the steel is heavier than the wood
c. warmer evening temperatures A.54
combined with cooler interior
temperatures 34. During the summer with clear sunny
d. lower heat capacity of water and days, clear nights and a diurnal
cooler evening temperatures temperature swing from 32 °C (90 °F) to
A.57; C.12-68 10 °C (50 °F), a lake and the surrounding
land would probably have the following
thermal relationship:
30. Which of the following is not a typical
pattern of an anomalous thermal image a. the land would be cooler than the lake
associated with wet roof insulation? at night
b. the land would be warmer than the
a. circular lake during the daytime
b. amorphous c. the land would be warmer than the
c. picture frame lake day and night
d. board type d. the land would be cooler earlier in the
H.5 evening then become warmer by
morning
A.57

34a 33a 32c 31b 30a 29a 28a 27c

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 Level I Questions: Thermal & Infrared Testing Method 5

35. The ratio of the radiant emittance of a 39. Which of the following is a commonly
given body to that of a blackbody is used technique to increase contrast in
defined as: thermal images?

a. radiance a. adjust camera to a higher temperature

b. reflectivity range
c. emissivity b. increase the span setting of the
d. transmissivity thermal image
A.38 c. use a gray monochrome palette
d. change to a multi-division color
36. Which of the following has the lowest palatte such as a rainbow
thermal conductivity? A.364

a. aluminum 40. Periodically most focal plane array

b. steel thermal imagers pause the live image and
c. wood go through an internal routine called
d. copper what?
A.57
a. non-uniformity correction
37. Which of the following camera b. internal temperature calibration
adjustments is used to optimize thermal c. thermal temperature correction
contrast of a thermal image? d. temperature uniformity calibration
E.45
a. focus
b. span 41. An appropriate thermal span and level
c. level setting for imaging a human face in a
d. range 22 °C (72 °F) room is:
C.12-61
a. 37 °C (98.6 °F)
38. Which of the following camera b. 27 to 38 °C (80 to100 °F)
adjustments will have an effect on c. 35 to 43 °C (95 to 110 °F)
temperature measurement? d. 13 to 22 °C (55 to 72 °F)
E.5
a. focus
b. span
c. level
d. palette
C.12-61

41b 40a 39d 38a 37b 36c 35c

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 6 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

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 Level II Questions: Thermal & Infrared Testing Method 7

Level II Questions
Thermal and Infrared Testing Method

1. Infrared cameras measure: 5. The plant’s main switchgear is to be

inspected. The main switchgear has new
a. the temperature of a surface aluminum busbar. The emissivity of new
b. the radiosity of a surface aluminum busbar is approximately:
c. the radiosity that is absorbed by the
detector in an infrared camera a. 1.0
d. the emittance of a surface b. 0.90
A.279 c. 0.50
d. 0.10
2. A camera has an IFOV of 1.9 mRad. A.36
What is its theoretical minimum spot size
at a distance of 100 cm? 6. What weather conditions are necessary
for conducting a thermal infrared roof
a. 1.9 cm inspection?
b. 0.19 cm
c. 0.019 cm a. it should have rained within 24 h,
d. 52 cm inspect during a sunny day
A.279 b. it must not have rained within the last
24 h, inspect during a sunny day
3. The slit response function is used to c. it must have rained within the last
measure: 24 h, inspect at night
d. it must not have rained within the last
a. field of view (FOV) 24 h, inspect after sundown following
b. IFOVmeasurement a clear sunny day
c. NETD H.4
d. MRTD
A.281 7. How should the level and span be set
when inspecting overhead electrical bus
4. What is the most important factor when plugs?
inspecting electrical equipment using IR?
a. set the camera to auto adjust mode
a. thermal sensitivity of the IR camera allowing the camera to adjust level
b. safety and span
c. image focus b. set the span wide for the full scene
d. thermal span and level and adjust level to the ambient
A.299 temperature
c. set span wide and allow the camera to
automatically adjust level
d. set the span very narrow and adjust
the level to the temperature of the bus
E.5

7d 6d 5d 4b 3b 2b 1c Answer key:

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 8 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

8. A thermal infrared inspection of a 12. When a thermal imaging radiometer is

building is conducted to determine the out of calibration and reading
presence of insulation. What is the temperatures incorrectly, what can be
recommended minimum temperature done to bring it back into radiometric
difference between inside and outside? calibration?

a. 3 °C (5 °F) a. perform an external non-uniformity

b. 5 °C (9 °F) correction (NUC)
c. 10 °C (18 °F) b. adjust the calibration with a calibrated
d. 20 °C (36 °F) blackbody reference source
G.6 c. send the camera back to the
manufacturer (or relevant body) for
9. An object that is not at thermal recalibration
equilibrium with its surrounding d. adjust the emissivity until the camera
environment is said to be: reads the correct temperature
A.293
a. at steady state
b. thermally isolated 13. The effects of the sun can prevent the
c. thermally transmissive accurate inspection of light frame
d. thermally transient buildings. In accordance with ASTM C
A.698 1060, how long should a wall of light
frame construction be free from direct
10. If the amount of insulation in an attic is solar radiation in order to conduct an
increased from 10 cm to 20 cm (3.94 in. infrared inspection of the wall?
to 7.87 in.) what effect does it have on the
conductive heat transfer? a. 1h
b. 3h
a. heat transfer will stay the same c. 8h
b. heat transfer will increase by 1/2 d. 12 h
c. heat transfer will be reduced by 1/2 G.6
d. heat transfer will increase by 2 times
A.54 14. A kilogram of each of the following
materials is heated to 90 °C (194 °F).
11. If the temperature difference from inside a Which of the following materials has the
house to outside the house decreases most stored thermal energy?
from 36 to 9 °C (64.8 to 16.2 °F), what
effect does it have on the conductive heat a. air
transfer through the walls? b. aluminum
c. steel
a. heat transfer will stay the same d. water
b. heat transfer will increase by four A.57
times
c. heat transfer will be reduced by four
times
d. heat transfer will be reduced by two
times
A.54

14d 13b 12c 11d 10c 9d 8c

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 Level II Questions: Thermal & Infrared Testing Method 9

15. Latent heat energy can be described as: 18. The accuracy of the liquid level gage on
the 946 353 L (250 000 gal) oil tank is
a. the energy that creates or breaks the being questioned. Verification of the
molecular bonds of the phase state of liquid level is critical but the safety
a material manager is not available to issue a
b. the energy that when added to a confined entry permit to physically verify
material will cause its temperature to the level. It is spring time. Last night was
increase cool and it is now noon and a bright
c. the energy released by a material that sunny day. What might you consider to
will cause its temperature to decrease determine the oil level?
d. the energy released by an object that
will break the molecular bonds of a a. Assume the liquid level indicator is
material correct unless definitive proof is
B.15 submitted otherwise.
b. Examine the tank with your infrared
16. Which of the following surfaces will camera. When you see no level
generally provide the most accurate indication between liquid and air it is
radiometric temperature measurement? safe to open the tank access door.
c. Examine the tank with your infrared
a. thin film plastic camera. The air should be warmer
b. oxidized aluminum than the liquid and should provide a
c. glass clear indication of the liquid level.
d. water-based paint d. Examine the tank with your infrared
A.36 camera. The air will be cooler than
the liquid and should provide a clear
17. The instantaneous field of view (IFOV) indication of the liquid level.
measurement of a radiometric system is A.290
1.2 mRad. What is the maximum size
object this system can accurately measure 19. How hot does an electrical connection
at a distance of 25 m? need to be for it to be a classified as a
serious problem?
a. 3m
b. 3 mm a. 1 to 5 °C (33.8 to 41 °F)
c. 3 cm b. 5 to 15 °C (41 to 59 °F)
d. 20.8 cm c. greater than 15 °C (59 °F)
A.279 d. depends on the criticality of
equipment to continued safe
operation
A.533

19d 18c 17c 16d 15a

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 10 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

20. Most imaging infrared radiometers 23. After heating one side of a honeycomb
operate in the 3 to 5 or 8 to 12 μm band. composite with a 4 ply graphite epoxy
This is because of: face sheet, and thermally viewing from
the same side, you notice a dark or cool
a. atmospheric reflection of solar indication that seems to be confined to a
radiation is adequately attenuated in group of honeycomb cells. What is the
these two bands probable cause of this thermal pattern?
b. the electromagnetic energy emitted by
a target outside these two bands is a. there is a disbond between the top
generally too small to provide usable sheet and the honeycomb cells
data b. there is a disbond between the bottom
c. atmospheric absorption within these face sheet and the honeycomb
two bands is small enough to provide c. there is most likely water or some
minimal impact on radiometry other liquid in the cells
d. technological limits of producing d. the honeycomb is most likely crushed
detectors with uniform characteristics A.57, 64
except for these two wave bands
A.80 24. From the ground you see a hot spot on a
1 in. (2.54 cm) bolted connector of a
21. Long wave (8-14 μm) infrared transmission line that is approximately
thermography is an excellent tool for 27.4 m (90 ft) away. When you go to
inspecting all except which of the measure the temperature, it reads much
following: lower than you think it should be, in fact
it appears to be below ambient. What is a
a. drive belts for proper alignment probable reason?
b. bearings for signs of impending
failure a. your IFOV is not turned on
c. thin film plastics b. you are not in focus
d. the temperature for creating baseline c. you are too far away to accurately
comparison measure
A.289 d. the emissivity is probably set
incorrectly
22. While doing an IR inspection of a heated A.295
stainless steel component with several
surface holes you notice that one of the 25. Thin film plastics, such as polyethylene,
holes appears hotter than the others. are thermally different from most
What could explain this? materials because they are:

a. that hotter hole is warmer than the a. highly reflective to short-wave

other holes thermal radiation
b. that hole must be reflecting b. highly absorptive to long-wave
something hotter than the other holes thermal radiation
c. the hotter hole must have more c. highly transmissive to both mid- and
thermal capacitance long-wave thermal radiation
d. the hotter hole probably is deeper d. opaque to both mid- and long-wave
than the other holes thermal radiation
A.123 A.291

25c 24c 23c 22d 21c 20c

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 Level II Questions: Thermal & Infrared Testing Method 11

26. Why is infrared thermal imaging often 30. To measure the temperature of heater
used by building analysts to locate mold tubes in a natural gas-fired furnace using
growth? a mid-wave sensing system you must:

a. mold is exothermic and appears a. add the correct filter

warmer on the surface b. set emissivity at 0.05
b. mold is endothermic and absorbs heat c. put a piece of tape on the heater tube
from surroundings, thus appearing d. mid-wave systems are not suitable for
warm furnace inspections
c. mold grows on damp surfaces, which A.573
appear cooler due to evaporative
cooling 31. You have found a motor bearing that is
d. mold is endothermic thus cooling the 32 °F warmer than normal. Convert this
surface temperature difference (ΔT) to degrees
D.15 Celsius.

27. Which of the following materials has the a. 0 °C

highest thermal capacitance? b. 17.7 °C
c. 89.6 °C
a. steel d. 100 °C
b. brick A.27
c. water
d. glass 32. Which of the following typically has the
A.57 greatest influence on taking a radiometric
temperature measurement on a
28. Which of the following factors will have low-emissivity object?
the greatest affect on the accuracy of a
temperature measurement of a loose a. background temperature
connection on a copper alloy bolted plate b. foreground air temperature
connection? Assume the copper has an c. distance to the target
emissivity of 0.28. d. relative humidity
A.296
a. estimating the copper has an
emissivity of 0.29 33. Which of the following camera settings
b. not setting relative humidity at 65% has the greatest impact on taking an
rather than the preset 50% accurate temperature measurement of an
c. leaving the distance to object set to object that actually has an emissivity of
3.05 m (10 ft) instead of 4.6 m (15 ft) 0.87, a background temperature of
d. not adjusting the background temp 23.9 °C (75 °F), relative humidity of 50%
from 76.6 °C (170 °F) to actual and distance to the object is 3.05 m
temperature of 28.3 °C (83 °F) (10 ft)?
A.289
a. relative humidity set at 40% instead of
29. Which of the following lists gives the 50%
correct order for the thermal capacitance b. distance to object set at 5.5 m (18 ft)
of the materials? Assume list goes from c. emissivity set at 0.72
highest to lowest thermal capacitance. d. background temperature set at
21.1 °C (70 °F) instead of 23.9 °C
a. steel, air, water (75 °F)
b. air, water, wood A.296
c. water, steel, air
d. water, air, steel
A.57

33c 32a 31b 30a 29c 28d 27c 26c

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 12 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

34. While conducting a roof moisture 38. The IR system being used stores images
inspection at night after a sunny day, why to videotape. Back in the office you find
is it important for the roof surface to be you’d like to adjust the level and span of
dry? an image. How is this accomplished?

a. evaporating water will mask the a. digitize the thermal image and adjust
thermal patterns below the roof the level and span in software
surface b. import the video into your
b. a dry roof surface is a better manufacturer’s software and adjust
conductor than a wet roof surface level and span
c. it is better to have a wet roof surface c. send the video to your camera
so you can find the leak easier manufacturer for conversion to 12 bit
d. a dry roof surface will radiate better data
to the cold sky d. data captured on videotape will not
H.4 allow the adjustment of level and span
A.361; B.12-61
35. Which of the following materials emits
quite differently in the mid-wave 39. The easiest and cheapest way to improve
(3.5-5 microns) band than in the the spatial resolution of a thermal image
long-wave band (8-14 microns)? is to:

a. plate glass a. buy a new imager with a detector that

b. polished aluminum has more detector elements
c. painted steel b. move the camera as close to the target
d. ceramic as possible without compromising
D.734 safety
c. install a telephoto lens
36. Using an infrared system with an d. defocus the lens
IFOVmeasurement ratio of 180:1. What is A.279, 297
the smallest size object you can
accurately measure at a distance of 3 m 40. Atmospheric attenuation for imaging
(3.3 ft)? systems that sense 8-12 microns thermal
radiation is:
a. 16.6 mm (0.65 in.)
b. 18.7 mm (0.74 in.) a. greater than the attenuation for
c. 50.0 mm (1.97 in.) 3-5 micron radiation
d. 166.0 mm (6.54 in.) b. less than the attenuation for
A.295 3-5 micron radiation
c. equal to the attenuation for
37. You are looking at an electrical 3-5 micron radiation
connection 20 m in the air. What IFOV d. greater than the attenuation for
measurement is required to accurately 6-8 micron radiation
measure the temperature on the 2.54 cm A.180
(1 in.) head of a bolt?

a. 0.125 mRad
b. 1.25 mRad
c. 2.5 mRad
d. 25 mRad
A.295

40b 39b 38d 37b 36a 35a 34a

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 Level II Questions: Thermal & Infrared Testing Method 13

41. When looking at a thermal image, the 45. The energy content of a gram of steam at
thermographer is viewing: 100 °C (212 °F) is much higher than that
of a gram of water at 100 °C (212 °F)
a. thermal patterns representing because of:
temperatures on the surface of the
target a. a 20 °C (68 °F) temperature difference
b. thermal patterns of objects reflected b. the latent heat of vaporization
from the surface of the target c. the additional shortwave thermal
c. radiance (combined reflected, radiation
transmitted and emitted energy) d. the latent heat of fusion
patterns from the surface of the target B.15
d. radiance (combined reflected,
transmitted and emitted energy) 46. The heat capacity of an object is:
patterns of objects reflected from the
surface of the object a. inversely proportional to the
A.89 material’s specific heat
b. directly proportional to a material’s
42. As a surface cools, the peak of its radiated specific heat and density
infrared energy: c. inversely proportional to its density
d. the ratio of short-wave infrared
a. shifts to longer wavelengths radiation absorbed by an object to
b. shifts to shorter wavelengths long-wave infrared radiation emitted
c. remains constant if emissivity remains by the object
constant A.57
d. remains constant even if emissivity
varies 47. What component of earth’s atmosphere
A.90 will completely or partially absorb
infrared electromagnetic energy in the
43. The spectral band in which glass wave band of 6-8 µm?
transmits infrared radiation most
efficiently is the ____ region. a. water vapor (H2O)
b. nitrogen (N) and oxygen (O2)
a. 2-4 μm combined
b. 5-7 μm c. oxygen (O2)
c. 6-10 μm d. nitrogen (N)
d. 10-15 μm A.180
A.291
48. Since wind will convectively cool
44. When water freezes: building components reducing thermal
differences, it is not advisable to perform
a. heat energy is absorbed from the building inspections on the windward
surroundings side when air speeds are in excess of:
b. the volume decreases and
conductivity increases a. 6 km/h (3.7 mph)
c. heat energy is released to the b. 12 km/h (7.5 mph)
surroundings c. 18 km/h (11 mph)
d. the volume increases and conductivity d. 24 km/h (15 mph)
decreases G.6
B.15

48d 47a 46b 45b 44c 43a 42a 41c

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 14 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

49. Which of the following statements 51. Distribution of energy over the
regarding infrared emission and wavelength spectrum for a given
absorption is false? temperature is best described by which of
the following?
a. good emitters are good absorbers
b. poor absorbers are poor emitters a. Planck’s Law
c. good reflectors are good emitters b. Stefan-Boltzmann Law
d. poor reflectors are good absorbers c. Newton’s Law
A.39 d. Fourier’s Law
A.90; C.14-49
50. Radiosity is defined as:

a. the perfect emittance of a blackbody

surface
b. detectivity/transmissivity
c. a graybody whose emissivity is less
than 1
d. the total radiant exitance leaving a
surface (reflectance, emittance and
transmittance)
A.89; C.12-62

51a 50d 49c

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 Level III Questions: Thermal & Infrared Testing Method 15

Level III Questions

Thermal and Infrared Testing Method

1. Energy is measured in units called: 4. Which device would be most appropriate

for measuring the surface temperature of
a. kelvin polyethylene film?
b. joule
c. watt a. a focal plane array radiometer with a
d. Rankine InSb detector (3 to 5 μm) cooled to
A.25 77 K (-196.15 °C)
b. a single element scanner with HgCdTe
2. You are asked to inspect a new paper detector (8 to 12 μm) cooled to
laminating process, with a long oven and 77 K (-196.15 °C)
stainless steel rollers, 91.44 cm (36 in.) c. infrared point radiometer filtered to
wide. The paper is laminated with a foil, detect 3.45 μm radiation
and only the foil side is visible as it curves d. calibrated bi-metal thermometer
around the stainless steel roller at the A.292
oven exit. It is important to ensure the foil
temperature is uniform at the oven exit 5. Liquid-in-glass thermometers are
for the adhesive to cure properly. What is designed and calibrated for three
the best way to ensure the material is conditions of use. Which of the following
cured? is not a condition of use for a
liquid-in-glass thermometer.
a. view the nip between the roller and
the foil with an infrared radiometric a. suspended immersion
imager b. total immersion
b. use a thermocouple to measure the c. partial immersion
moving foil temperature. d. complete immersion
c. use reflective radiometry to get an B.12-35
accurate temperature of the foil
d. increase the emissivity of the foil with 6. Which of the following nonuniformity
black paint corrections (NUC) will best provide both
A.122 uniform detector response and correct
for offset between the target signal and
3. When observing an object at 51.85 °C the detector response over the
(325 K), which of the following detectors temperature range of an active pulse IR
has the greatest detectivity (D*)? inspection?

a. HgCdTe (8 to 12 μm) cooled to a. one point external

-196.15 °C (77 K) b. one point internal
b. triglycene sulfate (8 to 12 μm) at c. two point external
ambient d. two point internal
c. InSb (3 to 5 μm) cooled to -196.15 °C E.45
(77 K)
d. PtSi (3 to 5 μm) cooled to -196.15 °C
(77 K)
A.188

6c 5a 4c 3c 2a 1b Answer key:

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 16 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

7. The energy emitted from a piece of metal 11. What is the correct value of the
is measured and the temperature is Stefan-Boltzmann constant?
determined to be 900 °C (1652 °F)
assuming a surface emissivity of 0.79. It is a. 5.67 × 10-8 W/cm
later found that the true emissivity is b. 5.67 × 10-12 W/m2
0.84. What is the closest temperature of c. 5.67 × 10-8 W/m2 ∙ K4
the metal from the values listed below. d. 5.67 × 10-8 W/cm2 ∙ K4
A.54
a. 918 °C (1684 °F)
b. 900 °C (1652 °F) 12. Wien’s displacement law for determining
c. 882 °C (1620 °F) the peak wavelength of emitted radiation
d 400 °C (752 °F) may be expressed as:
D.389
a. λmax = 2897/TK
8. Radiometric imagers of what wavelength b. λmax = TK ∙ 2897
should be used for accurate surface c. λmax = 2.897/TK
temperature measurement of plate glass? d. λmax = 289.77/TK
A.38
a. wavelengths less than 1.0 μm
b. wavelengths less than 4.5 μm 13. A change in the electrical resistance of
c. wavelengths greater than the responsive element in an infrared
4.5 μm detector due to temperature changes
d. wavelengths between 1.0 and produced by absorbed, incident infrared
2.4 μm radiation describes the:
A.291
a. thermovoltaic effect
9. Actual surfaces frequently exhibit b. photovoltaic effect
variable emissivities over the wavelength c. pyroelectric effect
spectrum. These surfaces are commonly d. bolometric effect
referred to as: A.21

a. real bodies 14. The slit response method is the generally

b. graybodies accepted method for determining
c. blackbodies IFOVmeasurement. What percent
d. white bodies modulation is required to obtain an
C.385 accurate temperature?

10. The peak spectral radiance from a a. greater than 90%

blackbody with a temperature of 1800 K b. less than 90%
(1526.85 °C) is: c. 50%
d. none of the above
a. equal to that of a blackbody at A.296
1800 °R (726.85 °C)
b. twice that of a blackbody at 900 K 15. Thermographic stress analysis is based
(626.85 °C) on which of the following effects that
c. less than that of a blackbody at 900 K relates dynamic changes in stress to the
(626.85 °C) temperature changes they produce:
d. greater than that of a blackbody at
900 K (626.85 °C) a. thermal conductivity effect
A.54 b. thermal diffusivity effect
c. thermoelastic effect
d. thermal gradient effect
A.325

15c 14a 13d 12a 11c 10d 9a 8c 7c

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Level III Questions: Thermal & Infrared Testing Method 17

16 Vibrothermography is a nondestructive 20. Heat is applied to the surface of a

test method that involves monitoring the 0.635 cm (0.25 in.) graphite epoxy
surface of a material with an infrared laminate. Which of the following
imager while the material is subjected to: statements are true?

a. forced mechanical oscillations a. when heat is applied evenly over the

b. thermal waves surface, heat flow will be
c. laser excitation multidirectional into the part
d. sudden thermal shock b. when heat is applied unevenly over
A.334 the surface, heat flow will be one
dimensional through the part
18. Thermal radiation is strongly absorbed c. when heat is applied evenly over the
by water vapor in which of the following surface, heat flow will be
wave bands? unidirectional through the part until a
discontinuity is reached
a. 3.5 to 5 μm d. when heat is applied evenly over the
b. 6 to 8 μm surface, heat flow will be
c. 9 to 10 μm multidirecynal through the part until
d. 10 to 12 μm a discontinuity is reached
A.180 B.54

18. The responsive element of infrared 21. You are asked to determine the minimum
detectors can be divided into what two defect size (surface indication) that can
groups? be resolved using a thermal imaging
system with an IFOV of 1.5 milliradians.
a. reflective detectors and emissive You are following ASTM 2582-07 which
detectors requires that nine contiguous pixels are
b. thermal detectors and photon projected within the boundaries of the
detectors indication. The minimum focus distance
c. static detectors and dynamic detectors of the thermal imager is 60.96 cm (24 in.).
d. quantitative detectors and qualitative Assuming the surface of the component
detectors has an emissivity of 0.94, what is the
A.274 minimum defect size that can be resolved
using the above system?
19. A good material for making a lens for an
infrared imager is a. 0.0914 cm (0.036 in.)
b. 0.1829 cm (0.072 in.)
a. germanium c. 0.2743 cm (0.108 in.)
b. graphite epoxy d. 0.9144 cm (0.36 in.)
c. indium antimonide A.279; I.2
d. glass
B.12-58

21c 20c 19a 18b 17b 16a

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18 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

22. How do you know that an active pulse 25. For the purpose of thermally locating
thermographic inspection of a material subsurface discontinuities, what is the
had sufficient power and inspection time? best method of applying heat to the
surface of an 8 ply carbon fiber face sheet
a. using the log plot, look for a break in to detect a delamination between ply 1
the straight line indicating heat hitting and 2?
the back wall
b. using full power on the flash lamps a. quartz lamps
will always provide sufficient power b. hot air gun
c. the peak contrast plot will indicate all c. incandescent heat lamp
possible indications are identified d. capacitor driven flash lamps
d. there is no way to determine sufficient A.376
power and time have been used
I.4 26. Thermal diffusivity is proportional to:

23. You are inspecting a 1 in. (2.54 cm) thick a. emissivity times reflectivity
aluminum panel that has been heated to b. heat capacitance
50 °C (122 °F). A small surface hole in the c. thermal conductivity divided by heat
panel appears warmer than the smooth capacitance
surface surrounding it. Why? d. spectral bandwidth divided by
responsivity
a. the crack or hole has a higher A.57
emittance
b. the surface emits less long wave 27. You suspect that a potential defect
thermal radiation indication in a sample may be due to a
c. the reflectivity of a crack or hole reflection from the flash lamp. What
equals 0.9999 should you do to determine if the
d. radiation is not emitted by aluminum anomaly was a defect or a reflection?
surfaces
A.123 a. unless the anomaly looks like a
reflection of the lamp it must be a
24. What is the best surface preparation for defect
using quartz lamps to conduct an active b. rotate the part and test again — if the
thermographic inspection of a composite anomaly moves with the part it is
component? probably a defect
c. do destructive analysis to see if the
a. optically reflective and thermally indication was a defect
reflective d. flip the part over and inspect from the
b. optically absorptive and thermally back side
emissive I.2
c. optically absorptive and thermally
neutral 28. When using solvent to clean a test piece
d. optically reflective and thermally for thermal evaluation it is important to:
emissive
A.122 a. be sure the solvent is dry for 5 min
before the inspect begins
b. be sure the solvent has fully
evaporated
c. be sure the piece has returned to
thermal equilibrium
d. never use solvents before thermal
NDT evaluations
B.15

28c 27b 26c 25d 24b 23a 22a

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Level III Questions: Thermal & Infrared Testing Method 19

29. According to ASTM E2582-07, as the 34. The minimum resolvable temperature
depth of a flaw increases, the size of the difference is a subjective measurement
minimum detectable flaw must: that depends on the:

a. remain the same a. infrared imaging systems spatial

b. increase resolution only
c. decrease b. infrared imaging systems thermal
d. elongate sensitivity and spatial resolution
I.2 c. infrared imaging systems
measurement resolution only
30. According to ASTM E2582-07, the optics d. infrared imaging system’s minimum
and the focal plane should be sufficient so spot size
that the projection of nine contiguous A.177
pixels onto the sample plane is:
35. The spatial resolution of an instrument is
a. greater than the minimum flaw area related to the:
b. equal to or greater than the minimum
flaw area a. instantaneous field of view and the
c. less than the minimum flaw area working distance
d. less than or equal to the minimum b. thermal resolution and the system
flaw area detectivity
I.2 c. spectral band width and the working
distance
31. According to ASTM E2582-07, the peak d. system responsivity divided by the
contrast time of a subsurface defect working distance
depends on which of the following: A.281

a. depth of the flaw 36. How does temperature affect the

b. orientation of the flaw wavelength of infrared peak emittance of
c. size of the flaw an object?
d. depth and size of the flaw
I.2 a. lower temperature objects have
shorter peak emittance wavelengths
b. higher temperature objects have
32. For high-speed imaging (in excess of shorter peak emittance wavelengths
60 frames per second), which of the c. temperature variations do not affect
following detector materials is most the wavelength of emitted radiation
appropriate: d. objects experiencing transient
temperatures will emit longer waves
a. PtSi when they are increasing in
b. pyroelectric vidicon temperature and shorter waves when
c. InSb they are cooling
d. mercury cadmium telluride F.6
A.191, 274
37. Of the following contact temperature
33. A pyroelectric vidicon is a ________ sensors, which is considered to be the
sensor. most accurate sensor?

a. photon a. RTDs
b. thermal b. thermocouples
c. bolometer c. thermistors
d. thermal/pressure d. liquid in glass thermometers
A.188 A.229

37a 36b 35a 34b 33b 32c 31d 30d 29b

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20 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

38. Which optical property changes due to 42. The energy emitted by an object radiates
temperature changes in liquid crystals? from a surface layer that is how thick?

a. absorptivity a. 3 to 4 μm
b. reflectivity b. 10 μm
c. transmissivity c. 100 μm
d. emissivity d. 200 to 400 μm
A.37 A.119

39. When heat is applied to an inspection 43. What are the two atmospheric gases that
surface for active nondestructive absorb transmitted radiation over the
evaluation of a material, a thermogram wave band of 1 to 15 μm?
will develop that is a function of the
material, the nature of the discontinuity, a. ozone and carbon dioxide
the heat intensity and: b. oxygen and ozone
c. water vapor and ozone
a. the time of observation d. water vapor and carbon dioxide
b. the wave band of the thermal imager A.180
used
c. the responsivity of the thermal 44. Minimum resolvable temperature
detector difference is a subjective measurement
d. surface roughness of the material that depends on the infrared imaging
A.37 system’s:

40. With respect to thermal nondestructive a. thermal sensitivity

testing, an empirical rule of thumb says b. spatial resolution
that the radius of the smallest detectable c. detectivity (D*)
discontinuity should be at least d. thermal sensitivity and spatial
_________ as its depth under the surface. resolution
A.177
a. one-quarter as large
b. one-half as large 45. You are asked to choose a thermal
c. as large imaging camera for a critical inspection
d. as large and preferably two or more of an aerospace component. If an
times as large anomaly is present it is expected to have a
A.43 very subtle signal with an MRTD about
75 mK. Expected surface temperature is
41. What is the term used to describe a in the vicinity of 350 K. Which of the
thermal NDT technique where following detectors will provide the
mechanical vibrations are externally greatest thermal contrast?
induced into a structure producing heat
caused by friction at discontinuities such a. vanadium oxide microbolometer
as cracks and delaminations? 8 to 12 μm
b. mercury cadmium telluride 8 to
a. ultrasonic thermography 12 μm
b. mechanically induced thermography c. lead selinide 3 to 5 μm
c. frictionally induced thermography d. indium antimonide 3.5 to 5 μm
d. vibrothermography A.182, 188
A.44-45

45d 44d 43d 42a 41d 40d 39a 38b

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Level III Questions: Thermal & Infrared Testing Method 21

46. When the radiant emission from a small 50. An important and critical assumption
opening in an isothermal enclosure is when using two-color pyrometers is that
examined, the spectral response is found a smooth curve exists between two
to closely approximate that of a: variables. What are these two variables?

a. spectral body a. roughness and color

b. colored body b. emissivity and wavelength
c. blackbody c. emissivity and temperature
d. graybody d. spectral translucence and emissivity
A.123 A.199

47. Which type of cryogenic cooling system 51. Compared to a thermocouple, an

for a photovoltaic type detector is advantage of a resistance temperature
perhaps the best choice for laboratory detector (RTD) is:
operation where reliability, quiet
operation, and low temperature are a. less expensive than a thermocouple
required? b. more linear than a thermocouple
c. wider temperature range than a
a. joule-thompson gas expansion using thermocouple
argon gas d. less stable than a thermocouple
b. sterling cooler using helium as A.229
coolant
c. liquid nitrogen in a metal dewar 52. One of the advantages of using
d. thermoelectric coolers using the thermocouples for temperature
peltier effect measurement over a resistance
A.182 temperature detector (RTD) is:

48. Which of following thermal detectors has a. thermocouples are more rugged
the highest detectivity (D*)? b. thermocouples are more stable
c. thermocouples are more accurate
a. InSb d. thermocouples are more linear
b. HgCdTe A.229
c. pyro-electric
d. microbolometer 53. One of the advantages of using a
A.188 resistance temperature detector (RTD)
over a thermocouple is RTDs:
49. A material that has a flat spectral
emissivity curve from 3-12 μm is a. have a wide temperature range
considered a: b. are self-powered
c. are more accurate
a. graybody d. are more rugged
b. colored body A.229
c. blackbody
d. spectral body 54. The seebeck effect is the basis for what
A.54, 197, 687 temperature measurement device?

a. liquid-in-glass thermometers
b. thermocouples
c. thermistors
d. resistance temperature detectors
A.231

54b 53c 52a 51b 50b 49a 48a 47c 46c

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22 Supplement to Recommended Practice SNT-TC-1A (Q&A Book): Thermal & Infrared Testing Method

55. You are asked to choose a surface 59. You are asked to measure the temperature
temperature measuring device that must of polyethelene at a temperature range
meet the following criteria: wide 80 to 90 °C (176 to 194 °F). What
temperature range, operate in a variety of waveband and with which filter will you
environments, simple to install, rugged choose to make these temperature
and relatively inexpensive. Which of the measurements?
following devices meets your
requirements the best? a. 3.4 to 5 μm with a 3.45 μm narrow
band pass filter
a. liquid-in-glass thermometers b. 3.4 to 5 μm with 4.8 μm high pass
b. resistance temperature detectors filter
c. thermistors c. 8 to 13 μm with 7.9 μm low pass filter
d. thermocouples d. 8 to 13 μm with a 10.3 μm narrow
A.235 band pass filter
A.292
56. What material is used as the primary
element in high-accuracy resistance 60. When capturing a series of thermal
thermometers? images that record a transient thermal
event, such as occurs with pulse heating
a. silver of a material to detect subsurface
b. triglycene sulfate anomalies, most of the rapid changes in
c. nickel the thermal evolution curve occur in the
d. platinum time interval immediately following
A.248 thermal excitation. It is beneficial to view
the thermal images using what type of
57. Distinguishing real temperature changes time scale?
from apparent temperature changes is one
of the biggest challenges facing infrared a. linear
thermographers. Apparent temperature b. logarithmic
changes can be caused by differences in c. exponential
all of the following except: d. statistical
A.363
a. emissivity
b. thermal diffusivity
c. transmissivity
d. target geometry
A.289

58. Which spectral range will you choose to

measure the temperature of an object
with a temperature range of 200 to
1000 °C (392 to 1832 °F), inside a heating
chamber with a glass viewing port?

a. 2 to 3 μm
b. 4 to 5 μm
c. 6 to 8 μm
d. 8 to 13 μm
A.291

60b 59a 59a 57b 56d 55d

ASNT grants non-exclusive, non-transferable license of this material to Bassam AbdElFattah AbdelAzeem.
All rights reserved. © ASNT 2024. To report unauthorized use, contact: customersupport@asnt.org
 A
Thermal & Infrared Testing Method
Questions & Answers Book

Q
Supplement to
Recommended Practice No. SNT-TC-1A
Book J

& Levels I, II and III

Review Questions

The American Society for

Nondestructive Testing, Inc. The American Society for
Catalog No.: 2025 Nondestructive Testing, Inc.
ASNT grants non-exclusive, non-transferable license of this material to Bassam AbdElFattah AbdelAzeem.
All rights reserved. © ASNT 2024. To report unauthorized use, contact: customersupport@asnt.org