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f humans cannot see ultraviolet waves, how can ultraviolet light be used to gather evidence of a crime?

Ultraviolet light detects the presence of radioactive substances.
Ultraviolet light shows cold areas as blue and warm areas as red.
Ultraviolet light causes substances to fluoresce and give off visible light.
Ultraviolet light transmits information to AM and FM radio receivers.

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Answered by GPT-5 mini AI
Ultraviolet light causes substances to fluoresce and give off visible light.

Explanation: Many biological fluids, certain inks, fibers, and other trace materials absorb UV and re-emit visible light, so using UV lamps makes them visible at a crime scene. The other choices are incorrect: UV doesn't detect radioactivity (Geiger counters do), showing temperatures as blue/red is infrared/thermal imaging, and UV isn't used to send signals to AM/FM radios.