History and Mechanism
Binocular, a small instrument which is used today for countless purposes was invented by Sir Galileo Galilei (an Italian scientist) in 1609. It was not really a binocular, but another form of it, a telescope.The underlying mechanism is same in both, simply put, there is some technical inter-play between different mediums (glass, water etc.) and the light that falls/passes through it and bends.
Basic Science of Binocular
This bending of the light is known as refraction, on the basis of which the whole working of binocular is found. In 19th century, this idea was further developed into a microscope to observe organisms not visible to a naked eye.
The colorful coatings on a binocular in addition to increasing its attractiveness is actually applied to prevent the loss of light when it changes medium. Military binoculars are the best for hunting and other such activities due to their special aspect of brightening an image in low light conditions that really helps during shady weather. Additionally, sniper binoculars were specifically made to measure the distance and height difference from the target object. Some of the toughest binoculars are for marines which are resistant to even the harshest weather and water proof (even total submersion).