INFRARED RADIATION A short history What is it?Application of infrared rays in our life
Short historyThe discovery of infrared radiation is ascribed toWilliam Herschel, the astronomer, in the early19thcentury. He used a prism to refract lightfrom the sun and detected the infrared beyond William Herschelthe red part of the Spectrum, through an increasein the temperature recorded on a thermometer.He was surprised at the result and called them prismcalorific rays. The term of infrared did notappear until late in the 19th century.
What is the infrared radiation?Infrared radiation (IR) is an electromagnetic radiation with a wavelength longer than that of visible light.Infrared radiation includes most of the thermal radiation emitted by objects near room temperature.Microscopically, IR light is typically emitted or absorbed by molecules when they change their rotational vibrational movements.
Much of the energy from the Sun arrives on Earth in the formon infrared radiation. Sunlight at zenith provides an irradianceof just over 1 kilo watt per square meter at sea level. Of thisenergy, 527 watts is infrared radiation, 445 watts is visiblelight, and 32 watts is ultraviolet radiation. The balance between absorbed and emitted infrared radiationhas a critical effect on the Earth’s climate
PracticalapplicationInfrared light is used inindustrial, scientific, and medicalapplication. Infrared imagingcameras are used to detectheat loss in insulatedsystems, observe changingblood flow in the skin, andoverheating of electricalapparatus.
In astronomy, imaging at infrared wavelengths allows observation of objects obscured by interstellar dust.Night-vision devices using infrared illumination allow people oranimals to be observed without the observer being detected
The Earth as infrared emitter The Earth’s surface and the clouds absorb visible and invisible radiation from the Sun and re-emit much of the energy as infraredback to the atmosphere. Certain substances in the atmosphere, chiefly cloud droplets and water vapor, but also carbon dioxide, methane, nitrous oxide, absorb this infrared and re-radiate it in all directions including back to Earth. Thus the greenhouse effect keeps the atmosphere and surface much warmer than if the infrared absorbers were absent from the atmosphere.
Infrared and greenhouse effect
Curiosities• Some animals (snakes, owls) can see infrared rays. This ability helps them to find food faster.• Infrared rays act deeply in our tissues. That’s why they are used as a method for losing weight. It is known as the most non-evasive therapy even for treating cancer.