Thermal/Infrared Testing (IR) Review Questions Flashcards
1
Q
1. Thermal resistance is: A. Analogous to electrical current B. A materials impedance to heat flow C. Proportional to the forth power of emissivity D. Proportional to the rate of heat flow
A
B. A materials impedance to heat flow
2
Q
- Conductive heat transfer cannot take place:
A. Across a vacuume
B. Within organic materials such as wood
C. Between two solid materials in contact
D. Between dissimilar metals
A
A. Across a vacuume
3
Q
- The infrared/thermal energy emitted from a target surface:
A. Occurs only in a vacuum
B. Is proportional to the forth power of the absolute surface temperature
C. Is inversely proportional to surface emissivity
D. Is totally absorbed by water vapor in the air
A
B. Is proportional to the forth power of the absolute surface temperature
4
Q
- Thermal radiation reaching the surface of a thermally opaque object will only be:
A. Absorbed by the surface
B. Absorbed and reflected by the surface
C. Reflected by the surface
D. Transmitted and absorbed by the surface
A
B. Absorbed and reflected by the surface
5
Q
5. The following spectral band is included in the infrared spectrum: A. 0.1 - 5.5 um B. 0.3 - 10.6 um C. 0.4 - 20 um D. 0.75 - 100 um
A
D. 0.75 -100 um
6
Q
- 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
A. Shifts to longer wavelengths
7
Q
7. A gray body 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
A
C. Almost a perfect reflector
8
Q
- 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
A
D. 0.20
9
Q
9. The spectral band in which glass transmits infrared radiation most efficiently is: A. 3-6 um region B. 2-3 um region C. 6-9 um region D. 9-11 um region
A
B. 2-3 um region
10
Q
- 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
A
A. Have a broad, flat spectral response
11
Q
- 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 specula reflecting surface
D. Highly transparent to infrared radiation
A
D. Highly transparent to infrared radiation
12
Q
- The minimum resolvable temperature difference is a subjective measurement that depends on:
A. The infrared imaging systems spatial resolution only
B. The infrared imaging systems thermal sensitivity and spatial resolution
C. The infrared imaging systems measurement resolution only
D. The infrared imaging systems minimum spot size
A
B. The infrared imaging systems thermal sensitivity and spatial resolution
13
Q
- The spatial resolution of an instrument is related to the:
A. Instantaneous field of view and the working distance
B. Thermal resolution
C. Spectral band width
D. System responsiveness
A
A. Instantaneous field of view and the working distance
14
Q
- The noise equivalent temperature difference (NETD) of an thermal infrared imager trends 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
A. Improve as the target temperature increases
15
Q
- The 3-5 um spectral region is well suited for the inspection of materials that exhibit:
A. Distance spectral characteristics limiting inspection to 3-5 um
B. Measuring targets at extremely long working distances
C. Measuring targets warmer than 392F
D. Operating at elevated ambient temperatures
A
C. Measuring targets warmer than 392F
16
Q
- When measuring the temperature of glass while using a mid-wave (3-5 um) infrared imaging system, which of the following steps is necessary?
A. Use a 3.2 um low pass filter
B. Use a 3.9 um band-pass filter
C. Use a 5 um high pass filter
D. No filter is necessary if using the same emissivity setting used with long-wave imaging systems
A
B. Use a 3.9 um band-pass filter
17
Q
- A line scanner is best used for applications:
A. Requiring online real-time process monitoring and control of a linear thermal process
B. Where the material is situationally
C. Where the process speed is no greater than 3 m/s
D. Where the maximum temperature of the material is 572F
A
A. Requiring online real-time process monitoring and control of a linear thermal process
18
Q
- 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 less diagnostic features than scanning radiometers
A
D. Offer less diagnostic features than scanning radiometers
19
Q
- When measuring the temperature of a non-gray target:
A. The viewing angle is not critical
B. Always assume a uniform emissivity
C. Varying surface temperature differences can be ignored
D. Errors may occur when using a variety of instruments
A
D. Errors may occur when using a variety of instruments
20
Q
- Thermal diffusivity is:
A. High for metals and low for pores materials
B. The same for all metals
C. Low for metals and high for porous materials
D. The same for all porous materials
A
A. High for metals and low for porous materials
21
Q
21. The term used to describe a materials surface temperature response to a given energy input is called: A. Diffuse reflectivity B. Thermal effusivity C. Thermal conductance D. Spectral transmittance
A
B. Thermal effusivity
