T/I

Question 1

1. 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.

Answer 1

b. a material’s impedance to heat flow.

Question 2

2. Conductive heat transfer can take place:
   a. across a vacuum.
   b. from a hair dryer blowing on an object.
   c. between a heat lamp and a distant object.
   d. between dissimilar metals in contact with each other.

Answer 2

d. between dissimilar metals in contact with each other.

Question 3

3. The infrared/thermal energy emitted from a target surface:
   a. occurs only in a vacuum.
   b. is inversely proportional to surface emissivity.
   c. is proportional to the fourth power of the absolute
   surface temperature.
   d. is totally absorbed by water vapor in the air.

Answer 3

c. is proportional to the fourth power of the absolute
surface temperature.

Question 4

4. 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

Answer 4

b. absorbed and reflected by the surface.

Question 5

5. The following spectral band is included in the infrared spectrum:
   a. 0.1 to 5.5 μm
   b. 0.3 to 10.6 μm
   c. 0.4 to 20 μm
   d. 0.75 to 100 μm

Answer 5

d. 0.75 to 100 μm

Question 6

6. 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.

Answer 6

a. shifts to longer wavelengths.

Question 7

7. 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.

Answer 7

c. almost a perfect reflector.

Question 8

8. 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.

Answer 8

d. 0.20.

Question 9

9. The spectral band in which glass transmits infrared
   radiation most efficiently is the:
   a. 3 to 6 μm region.
   b. 2 to 3 μm region.
   c. 6 to 9 μm region.
   d. 9 to 11 μm region.

Answer 9

b. 2 to 3 μm region.

Question 10

10. 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

Answer 10

a. have a broad, flat spectral response.

Question 11

11. 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. highly transparent to infrared radiation.

Answer 11

b. a surface that scatters reflected energy in many
directions.

Question 12

12. The minimum resolvable temperature difference is a subjective measurement that depends on:
    a. the infrared imaging system’s spatial resolution only.
    b. the infrared imaging system’s measurement resolution only.
    c. the infrared imaging system’s thermal sensitivity and spatial resolution.
    d. the infrared imaging system’s minimum spot size.

Answer 12

c. the infrared imaging system’s thermal sensitivity and spatial resolution.

Question 13

13. The spatial resolution of an instrument is related to the:
    a. thermal resolution.
    b. spectral bandwidth.
    c. system responsivity.
    d. instantaneous field of view and the working distance.

Answer 13

d. instantaneous field of view and the working distance.

Question 14

14. The noise equivalent temperature difference (NETD) of a thermal infrared imager 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.

Answer 14

a. improve as the target temperature increases.

Question 15

15. The 3 to 5 μm spectral region is well suited for:
    a. inspection using a microbolometer.
    b. measuring targets at extremely long working distances.
    c. measuring targets warmer than 200 °C (392 °F).
    d. operating at near ambient temperatures.

Answer 15

c. measuring targets warmer than 200 °C (392 °F).

Question 16

16. When measuring the temperature of glass while using a mid-wave (3 to 5 μm) infrared imaging system, which of the following steps is necessary?
    a. Use a 3.2 μm low-pass filter.
    b. Use a 5 μm high-pass filter.
    c. No filter is necessary if using the same emissivity
    setting used with long-wave imaging systems.
    d. Use a 3.9 μm bandpass filter.

Answer 16

d. Use a 3.9 μm bandpass filter.

Question 17

17. 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 stationary.
    c. where the process speed is no greater than 3 m/s.
    d. where the maximum temperature of the material is
    300 °C (572 °F).

Answer 17

a. requiring online real-time process monitoring and
control of a linear thermal process.

Question 18

18. 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 diagnostics features than scanning
    radiometers.

Answer 18

b. offer better spatial resolution than scanning
radiometers.

Question 19

19. When measuring the temperature of a nongray 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

Answer 19

d. errors may occur when using a variety of instruments

Question 20

20. 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

Answer 20

a. high for metals and low for porous materials.

Question 21

21. The term used to describe a material’s surface temperature response to a given energy input is called:
    a. diffuse reflectivity.
    b. thermal conductance.
    c. thermal effusivity.
    d. spectral transmittance.

Answer 21

c. thermal effusivity.