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.

the circled areas are referred to   as sunspots.   the sunspots are cooler than the   surrounding area.

sunspots are temporary phenomena on the photosphere of the sun that appear visibly as dark spots compared to surrounding regions. they correspond to concentrations of magnetic field flux that inhibit convection and result in reduced surface temperature compared to the surrounding photosphere.

answer; convade;