How is infrared radiation used in photography?

Understanding infrared - definition and practical uses

Electromagnetic waves in a specific spectral range are referred to as infrared radiation, often simply referred to as thermal radiation. Infrared radiation can come from natural sources such as the sun. The radiation is also emitted by ovens, infrared heaters or special infrared emitters. But what exactly is infrared radiation? What are the different areas of application? Can infrared radiation be harmful? In our guide below, we have summarized a lot of interesting information about infrared radiation for you in an easily understandable way.

What is infrared radiation exactly?

Infrared radiation cannot be perceived by the human eye. When you sunbathe or spend a cozy evening under a radiant heater, you can feel infrared radiation in the form of warmth on your skin. Various rays such as X-rays, microwaves, UV rays, visible light and infrared radiation are included in the electromagnetic radiation spectrum in physics. This is divided into wavelengths, among other things. By definition, infrared covers the range between 780 nanometers and 1 millimeter. The wavelength of infrared radiation lies in the range between visible light and microwaves. Microwaves are generated, among other things, by microwave ovens for heating food. Infrared rays can be further divided according to their wavelength:

  • 780 to 1400 nanometers: short-wave IR-A radiation
  • 1400 to 3000 nanometers: IR-B radiation with medium wavelength
  • 3000 nanometers to 1 millimeter: long-wave IR-C radiation

In some cases, infrared radiation is simply divided into the categories near, medium and far infrared. While the wavelength of near infrared radiation is very close to visible light, the wavelength of far infrared light is almost at the level of microwaves. The heat radiation perceived by humans is mostly in the range of mid-infrared radiation, while films that can depict near-infrared light are used for special photographs.

Which sources are used to emit infrared radiation?

The greatest source of natural infrared radiation is the sun. Like other types of radiation emitted by the sun, infrared radiation travels to earth at the speed of light (approx. 300,000 km per second). As a result, the warming rays of the sun need a good eight minutes to reach the earth. Infrared radiation makes up about 50 percent of the rays emitted by the sun. In general, infrared radiation is given off by all warm objects. In the context of physics, “warm” already means a temperature above absolute zero of - 273 ° C. According to this definition, ice or snow also emit thermal radiation. The intensity or amount of the emitted infrared radiation depends on the temperature of the object. The warmer an object is, the more thermal radiation it emits. Typical sources of infrared radiation in everyday life are, for example, radiators, fireplace stoves, hotplates or special infrared heaters.