What is the name for the portion of the electromagnetic spectrum with wavelengths ranging from 700 nanometers to 1 millimeter?

• A. Ultraviolet
• B. Microwave
• C. Visible light
• D. Infrared band

Answer: (D)

Wavelengths from 700 nanometers to 1 millimeter sit in the infrared portion of the electromagnetic spectrum. This region lies just beyond the red end of visible light and includes near-infrared up to about a few hundred micrometers and extending to about 1 millimeter. Humans can’t see infrared, but it’s widely used for thermal imaging and night-vision sensing. Ultraviolet is shorter than visible light, and visible light is roughly 400–700 nanometers, so those don’t match this range. Microwaves start at around 1 millimeter and extend longer, so the entire 700 nanometers to 1 millimeter span is best described as the infrared band.