Which of the following ranges correctly identifies long-wave infrared wavelengths?

• A. 4000-8000 mu
• B. 800-1500 mu
• C. 1500-12,000 mu
• D. 4000-8000 A

Answer: (C)

Long-wave infrared wavelengths lie at the longer end of the infrared spectrum, typically around the 8–12 micrometer range (with some definitions extending into higher micrometers). Among the options, the range that uses micrometers and extends far enough to cover the LWIR region is the one that runs from 1,500 to 12,000 micrometers. This span includes the common LWIR window around 8–12 micrometers, making it the best match for long-wave infrared. The other ranges point to visible light (angstroms), near-infrared (about 0.8–1.5 micrometers), or mid-infrared (about 4–8 micrometers) and do not align with the long-wave infrared band as a whole.