Question

if 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.

Explanation:

Ultraviolet light has a specific property where it can cause certain substances (like some bodily fluids, dyes used in forensics) to fluoresce. Fluorescence means these substances absorb the ultraviolet light and then emit visible light. This emitted visible light can be seen by humans. Radioactive substances are detected using different methods (like Geiger - Muller counters, not ultraviolet light). The description of cold as blue and warm as red is related to infrared imaging (not ultraviolet). Ultraviolet light is not used for transmitting information to AM/FM radio receivers (radio waves are used for that).

Answer:

Ultraviolet light causes substances to fluoresce and give off visible light.