Help
electromagnetic spectrum — English
All matter with a temperature higher than absolute zero (-273° Kelvin or -495,4° Fahrenheit) radiate electromagnetic energy in the form of waves with different wavelengths. The light from the sun consists of a wide spectrum of frequencies. Some of these fall in the spectrum which our eyes can detect, namely the visible spectrum. All other frequencies of light cannot be detected by the human eye. All wavelengths ranging from 0,4 micron to 0,7 micron fall within the visible spectrum. Shorter wavelengths are invisible ultra-violet and X-rays, and those longer than 0,7 microns are invisible infrared rays, microwaves and radiowaves. Although our eyes cannot see wavelengths that fall outside of the visible spectrum, certain types of films and other light sensitive remote sensing devices can detect some of those frequencies. Although the human eye that is looking through the camera to take a photograph can only detect the visible spectrum of light frequencies, the film in the camera can detect more than the eye that is looking through the camera. One common example of light frequencies that the human eye cannot see is short wave X-rays which are part of standard medical diagnostic technology and healthcare without X-rays is hardly imaginable anymore. Likewise, spatial research without the aid of the long wavelengths of infrared rays have revolutionised the use of photography in geographical investigation. Remote sensing images of the Earth’s surface from a very great distance by infrared sensitive remote sensing devices mounted in satellites has become an extremely important standard geographical tool and it even forms a specialisation field within the science of geography. Spatial research without the aid of such imagery is as unimaginable as medical science without X-ray photography.
