Infrared-
Infrared light sits between the visible and microwave portions of the electromagnetic spectrum. Heat is transferred from the sun as Infared radiation. They're given this name, not becasue they are red but because they are next to red light on the visible spectrum. "Infra" means below and infrared radiation has a lower frequency than red light. You cannot see this type of radiation but feel its warmth on your skin.
All objects with a temperature above 0 Kelvin emit infrared radiation. The hotter the object the more infrared radiation that is released. Infrared radiation can be detected by using a infrared camera.
Some objects are so hot they emit visible light—like how a fire does. Other objects, such as humans, are not as hot and only emit only infrared waves. Our eyes cannot see these infrared waves but instruments that can view infrared energy—such as night-vision goggles or infrared cameras–allow us to "observe" the infrared waves emitted from warm objects such as humans and animals.
All objects with a temperature above 0 Kelvin emit infrared radiation. The hotter the object the more infrared radiation that is released. Infrared radiation can be detected by using a infrared camera.
Some objects are so hot they emit visible light—like how a fire does. Other objects, such as humans, are not as hot and only emit only infrared waves. Our eyes cannot see these infrared waves but instruments that can view infrared energy—such as night-vision goggles or infrared cameras–allow us to "observe" the infrared waves emitted from warm objects such as humans and animals.
In 1800, William Herschel conducted an experiment measuring the difference in temperature between the colours in the visible spectrum. He placed thermometers within each colour of the visible spectrum. The results showed an increase in temperature from blue to red. When he noticed an even warmer temperature measurement just beyond the red end of the visible spectrum, Herschel had discovered infrared light!
~Segment from http://missionscience.nasa.gov/ems/07_infraredwaves.html
In today's society we use:
Night Vision (goggles)
Nightvision is used to see in the dark. Humans cannot do so without the use of a nightvision device. They are commonly used by military personel, and even people watching animals in dark places or at night.
How do nightvision goggles work?
Dim light from a night scene enters the lens at the front. The light is made of photons (particles of light) of all colors.
As the photons enter the goggles, they hit a light-sensitive surface called a photocathode. It's similar to a very precise solar panel: it's job is to convert the photons into electrons.
The electrons are amplified by a photomultiplier, a kind of photoelectric cell. Each electron entering the photomultiplier results in many more electrons leaving it.
The electrons leaving the photomultiplier hit a phosphor screen. As the electrons hit the phosphor, they create tiny flashes of light.
Since there are many more photons than originally entered the goggles, the screen makes a much brighter version of the original scene.
Why does everything look green through night vision goggles?
Even at night, the photons that hit the lens at the front of night vision goggles are carrying light of all colours. But when they are converted to electrons, there's no way to preserve that information. Hence, the incoming, coloured light is turned into black and white. It's easier to look at green screens for long periods than to look at black and white ones (that's why early computer screens tended to be green). Thus, night vision goggles have their characteristic; the green glow.
Night Vision (goggles)
Nightvision is used to see in the dark. Humans cannot do so without the use of a nightvision device. They are commonly used by military personel, and even people watching animals in dark places or at night.
How do nightvision goggles work?
Dim light from a night scene enters the lens at the front. The light is made of photons (particles of light) of all colors.
As the photons enter the goggles, they hit a light-sensitive surface called a photocathode. It's similar to a very precise solar panel: it's job is to convert the photons into electrons.
The electrons are amplified by a photomultiplier, a kind of photoelectric cell. Each electron entering the photomultiplier results in many more electrons leaving it.
The electrons leaving the photomultiplier hit a phosphor screen. As the electrons hit the phosphor, they create tiny flashes of light.
Since there are many more photons than originally entered the goggles, the screen makes a much brighter version of the original scene.
Why does everything look green through night vision goggles?
Even at night, the photons that hit the lens at the front of night vision goggles are carrying light of all colours. But when they are converted to electrons, there's no way to preserve that information. Hence, the incoming, coloured light is turned into black and white. It's easier to look at green screens for long periods than to look at black and white ones (that's why early computer screens tended to be green). Thus, night vision goggles have their characteristic; the green glow.