Irradiation

[Sarah]

The apparent enlargement of a bright object seen upon a darkground, due to the fact that the portions of the retina around theimage are stimulated by the intense light; as when a dark spot on awhite ground appears smaller, or a white spot on a dark groundlarger, than it really is, esp. when a little out of focus.

[Rihanna]

light or other types of radiation used in order to treat or diagnose a medical condition:

[Little_Girl]

The process or fact of irradiating or being irradiated.