You probably know that you should wear sunscreen at the beach because of dangerous ultraviolet rays, but do you know what ultraviolet rays are? Can you see them? Maybe you've also heard about infrared sensors used for detecting heat. But what is infrared?
Ultraviolet rays and infrared are types of radiant energy which are outside of the human range of vision. The diagram below shows the entire electromagnetic spectrum from high frequency, short-wavelength gamma rays to low frequency, long-wavelength radio waves. Humans can only see a very small part of the electromagnetic spectrum, the visible spectrum (think of a rainbow).
Many insects are able to detect wavelengths that humans are not able to see. Bees, for example, can detect three colors: ultraviolet, blue, and yellow, but not red. The ability to see red is actually rare for all insects. The butterfly is an exception to this rule. Butterflies are believed to have the widest visual range of any animal. Various species of butterfly can detect wavelengths anywhere from 310 nm to 700 nm. To humans, male and female butterflies may look the same, but butterflies are able to identify each other easily because of ultraviolet markings on their wings. Butterflies and insects are also attracted to ultraviolet nectar of certain flowers. The photos below other simulate how humans, bees, and butterflies see the same flower.
|Human Vision||Bee Vision Simulation||Butterfly Vision Simulation|
The ability to detect light beyond the visible spectrum is not only helpful to insects. Humans can benefit from seeing non-visible wavelengths as well. How is this if we can only see visible light? Let's learn more. (continue on to Invisible Light)