Infrared
Introduction
Infrared (IR) is a type of electromagnetic radiation that sits between the visible light spectrum and microwave radiation in terms of wavelength. It is invisible to the human eye, but can be detected as heat. The term 'infrared' means 'below red', referring to its position in the electromagnetic spectrum.
Discovery
The discovery of infrared radiation is credited to Sir William Herschel, a German-born British astronomer, in the early 19th century. Herschel conducted an experiment using a prism to refract light from the sun and an instrument called a thermometer to measure the heat of the different colors. He noticed that the temperature increased towards the red end of the spectrum, and even more so beyond the red light, where no visible light was present. This led him to the discovery of a new type of light, which he named 'infrared'.
Characteristics
Infrared radiation has wavelengths ranging from approximately 700 nanometers (nm) to 1 millimeter (mm), which places it between visible light and microwave radiation on the electromagnetic spectrum. It is further divided into near, mid and far-infrared, each with distinct properties and applications.
Near Infrared
Near infrared (NIR) has wavelengths ranging from 700 nm to 1400 nm. It is the closest infrared light to the visible light spectrum and has similar properties to visible light, such as its ability to be focused and reflected.
Mid Infrared
Mid infrared (MIR) ranges from 1400 nm to 3000 nm. It is emitted by objects at temperatures typical of the Earth's surface and is absorbed by many atmospheric gases, making it useful in a variety of applications such as environmental monitoring and thermal imaging.
Far Infrared
Far infrared (FIR) has wavelengths from 3000 nm to 1 mm. It is emitted by objects at lower temperatures and is strongly absorbed by water, making it useful in applications such as weather forecasting and astronomy.
Applications
Infrared radiation has a wide range of applications in various fields, including but not limited to, medicine, astronomy, telecommunications, and meteorology.
Medicine
Infrared radiation is used in various medical applications, such as thermography, where an infrared camera is used to detect heat patterns and blood flow in body tissues. It is also used in physiotherapy to provide deep heating to treat conditions such as arthritis and muscle pain.
Astronomy
Infrared astronomy uses infrared radiation to study celestial objects. This is particularly useful as infrared light can penetrate dust clouds in space, allowing astronomers to observe objects that would otherwise be obscured.
Telecommunications
Infrared is used in wireless communication technologies, such as remote controls and wireless networks. Infrared data transmission is also used in short-range communication between computers and peripheral devices.
Meteorology
Infrared satellite imagery is used in meteorology to monitor weather patterns. This is because clouds and precipitation emit infrared radiation, which can be detected by satellites to provide a picture of the Earth's weather.