Tell about Infrared ?

Wavelength and frequency

Electromagnetic (EM) radiation is transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic spectrum.

The global image on the right is an infrared image of the Earth taken by the GOES 6 satellite in 1986. A scientist used temperatures to determine which parts of the image were from clouds and which were land and sea.

The spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency.

The common designations are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays.

While it is easier to distinguish clouds from land in the visible range, there is more detail in the clouds in the infrared.

Infrared sensing

One of the most useful applications of the IR spectrum is in sensing and detection. All objects on Earth emit IR radiation, or heat, which can be detected by electronic sensors, such as those used in night-vision goggles and infrared cameras. A simple example of such a sensor is the bolometer, which consists of a telescope with a temperature-sensitive resistor, or thermistor, at its focal point.

If a warm body comes into this instrument's field of view, the heat causes a detectable change in the voltage across the thermistor. Night-vision cameras use a more sophisticated version of a bolometer.

These cameras typically contain charge-coupled-device (CCD) imaging chips that are sensitive to IR light. The image formed by the CCD can then be reproduced in visible light.

These systems can be made small enough to be used in hand-held devices or wearable night-vision goggles. They can also be used for gun sights with or without the addition of an IR laser for targeting.

Infrared astronomy

The California Institute of Technology (CalTech) describes infrared astronomy as "the detection and study of the infrared radiation (heat energy) emitted from objects in the universe.

Advances in IR CCD imaging systems have allowed for detailed observation of the distribution of IR sources, revealing complex structures in nebulae, galaxies and the large-scale structure of the universe.

What is infrared used for?

All objects on Earth emit IR radiation, or heat, which can be detected by electronic sensors, such as those used in night-vision goggles and infrared cameras.

We know, from looking at an infrared image of a cat, that many things emit infrared light. But many things also reflect infrared light, particularly near infrared light. Learn more about REFLECTED Near-infrared radiation.

A simple example of such a sensor is the bolometer, which consists of a telescope with a temperature-sensitive resistor, or thermistor, at its focal point.

Infrared radiation is a type of electromagnetic radiation, as are radio waves, ultraviolet radiation, X-rays and microwaves. Infrared (IR) light is the part of the EM spectrum that people encounter most in everyday life, although much of it goes unnoticed.

According to the Environmental Protection Agency, incandescent bulbs convert only about 10 percent of their electrical energy input into visible light energy; about 90 percent is converted to infrared radiation.

A TV remote control uses IR waves to change channels. In the remote, an IR light-emitting diode (LED) or laser sends out binary coded signals as rapid on/off pulses, according to NASA.

A detector in the TV converts these light pulses to electrical signals that instruct a microprocessor to change the channel, adjust the volume or perform other actions.

Light comes to Earth in waves. Some of the waves are long. Some of the waves are short. The waves are all different in their size. We can see some of the waves in the form of color. But other waves we cannot see with our eyes. But we can see them with special cameras.

Infrared light is one of the lights we can see with special cameras. Infrared light shows us how hot things are. It can also show us how cold things are. But it all has to do with heat.

One of the advantages of IR observation is that it can detect objects that are too cool to emit visible light. This has led to the discovery of previously unknown objects such as comets, asteroids and wispy interstellar dust clouds that seem to be prevalent throughout the entire galaxy.

IR astronomy is particularly useful for observing cold molecules of gas and also dust particles in the interstellar medium to determine their chemical makeup, said Robert Patterson, professor of astronomy at Missouri State University.

Another advantage of IR radiation is that because of its longer wavelength, it is less subject to scattering than is visible light. Whereas visible light can be absorbed or reflected by gas and dust particles, the longer IR waves simply go around these small obstructions.

With special infrared cameras, you can see the heat. It makes things that are hot look like they are glowing. In infrared light, hot things look bright yellow and orange. Items that are colder, such as an ice cube, are purple or blue.