Infrared Light is useful to us because Slightly more than half of the energy from the sun arrives on Earth in the form of infrared radiation and nearly everything around us gives off some form of infrared light. Infrared light has a wavelength that is a little longer than that of the red light than we can see and it is not visible to human eyes. However many animals like piranha fish the live in the murky waters of the Amazon river have the ability to detect infrared light. Some insects too have antennae that can detect infrared light and this lets them see in dark.
Today research scientists are developing devices using infrared light that have many uses both for military and in everyday life. Night vision devices using active near infrared illumination allow people or animals to be observed without the observer being seen. Infrared light is used in industrial, scientific and medical applications. So, though infrared or “IR” is just out of range of what the human eye can detect, we can still use infrared light to see things.