Ultraviolet or all wavelengths
In water molecule the electrons between the oxygen and the hydrogen are shared, but the sharing is not equal. Oxygen pulls electrons slightly towards itself. Therefore, the electrons are more near the oxygen, making that part of molecule(oxygen part) slightly negative. Since the electrons are not near the hydrogen so, that part of the molecule is slightly positive.
The answer to this question is "PERCEPTION". The term refers to the mental capacity that process of sorting out things, interpreting things mentally, analyzing things and conditions, and integrating stimuli from the sense organs and from the brain and later come up in a concrete and the sensible result after mental processing.
