Driver's vision enhancer and DRS Technologies. All objects above Absolute zero (−273.15 °C / −459.67 °F) emit infrared radiation (IR), an invisible form of light beyond the optical spectrum. The optical spectrum is part of the electromagnetic energy spectrum which consists of ultraviolet, visible, and near, middle, and far-infrared energy. Only a small part of the optical spectrum is visible to the unaided eye. The Sun emits energy across the entire electromagnetic spectrum. Solar energy strikes the surface of objects. Some of that energy is absorbed and stored as heat (thermal energy). After sunset, this thermal energy remains and is emitted in the
Ultraviolet communication in butterflies to detect UV light and responds maximally to ultraviolet light at approximately 350 nm. Therefore, a visual pigment that responds to ultraviolet light is the mechanism behind ultraviolet light perception. White Cabbage Butterflies, "Pieris rapae crucivora", use their private ultraviolet communication system to initiate mating behavior. In this species, ultraviolet reflection is sexually dimorphic with females exhibiting the ability to reflect ultraviolet light of 380 nm to 400 nm and males being less able to reflect UV. Males who perceive an ultraviolet reflection from a female initiate a courtship behavior that involves approaching the female and attempting to copulate. Females