You're reading your favorite mystery novel. You're just about to discover who the culprit was when suddenly, the lights went out. Frustrating, isn't it? How you wish you have one of those goggles you see on the television that allows you to see even it was dark. But do you think this things really works?
They definitely do. Night vision goggles (NVG) are instruments that allows you to see in the dark. I thought it was just on the movie. But some NVG let you see a person standing more than 180 meters away on a cloudy, moonless night. NVG are often used by the military. They are also used by scientists studying wildlife that are active at night.
There are two common types of NVG. Passive NVG work by collecting tiny amounts of light present in an area,then amplifying these several thousand times using a device called an image intensifier.
An image intensifier increases the amount of visible light from an image so that a dimly-lit scene can become visible to a person or a camera. It does not work in complete darkness where there would be no light intensify.
Passive NVG often show images that are tinted in green. Green is used because people's eyes are most sensitive to this color and could distinguish most shade of green.
The second type, active NVG, project infrared light that is reflected back. IR is the same type of light used by remote controls. It is emitted as heat instead of being simply reflected as light. Hotter objects, such as living bodies,emit more IR than cooler objects like tables, or houses. Images seen through active NVG appear in different shades, depending on how hot they are.
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