SPACEKIDS LOGO

The electromagnetic spectrum spans a wide range of wavelengths from very short wavelength and highly energetic gamma rays to very long wavelength and low-energy radio waves. The visible part of the spectrum is only a small portion. Infrared light is the same as the light that we can see except that the wavelength is longer and outside the range that our eyes can sense.

The electromagnetic spectrum

The electromagnetic spectrum
The electromagnetic spectrum. Click image for higher resolution.

Electromagnetic radiation from objects at different temperatures

All objects emit electromagnetic radiation, and the wavelength region over which they emit radiation depends on the temperature of the object. The diagram below shows how the brightness of objects at different temperatures varies as a function of wavelength. The colder an object is, the longer the peak wavelength of emission.

Black bodies at various temperatures
The Sun has a surface temperature of nearly 6000 Kelvin (where the Kelvin temperature scale is the same as the familiar Centigrade scale except that the zero degrees C is about 273 degrees Kelvin). Its radiation peaks in the visible part of the spectrum at wavelengths of about half a micron, as shown by the green line in the graph to the right.




Portrait ot William Herschel and his infrared experiment
Infrared radiation was discovered by William Herschel in 1800. He was studying the heating effect of different colours of light by using a prism to produce a spectrum of colours and thermometers to measure their heating effect. He noticed that the heating effect got stronger as he went from the blue end of the spectrum to the red. In a moment of inspiration, he moved the thermometer beyond the visible red end and found that the heating effect was even greater.

It is interesting that the basic technique used by Herschel to discover infrared radiation is still used in modern instruments today, including instruments on board the Herschel satellite – the only real difference is a factor of a billion or so in sensitivity.

The whole region with wavelengths ranging from 1 micron to 1 mm is loosely called the “infrared”, but scientists tend to break this up into sub-regions:  the “near infrared” (from 1 to 5 microns); the “mid infrared” (5 to 30 microns), the “far infrared” (from 30 to 300 microns) and the “submillimetre” (from 300 microns to 1 mm).  The boundaries are somewhat arbitrary, and the exact definitions can vary.

Humans, slightly warmer than room temperature, glow in the mid infrared and we’re brightest at about 10 microns wavelength (black line in the graph). The pictures below show a colleague, Prof. Peter Ade, in visible light (wavelength about 0.5 micron) and infrared light (about 10 microns). The key difference in these images is that the visible image (left) records short wavelength light (daylight) reflected off his face. The IR image (right) records light that is emitted from his body and clothing, as a result of it's temperature. Note that the light emitted from his face is blocked by his glasses. Glass becomes opaque in the infrared region.

Clouds of interstellar gas and dust that form stars are typically at temperatures of about 50 K (that’s about –220oC). They glow at far infrared wavelengths and are brightest at about 100 microns (red line in the graph above).  And the universe itself is filled with radiation corresponding to a temperature of just less than 3 K, with peak emission in the millimetre wavelength range (blue line in the graph above).

2nd SPACEKIDs workshop

2nd international SPACEKIDs Workshop

The second, and final community workshop will be held on 10th March at the European Space Technology Centre, Noorwijk, Netherlands.

 

2nd SPACEKIDs workshop

2nd international SPACEKIDs Workshop

The second, and final community workshop will be held on 10th March at the European Space Technology Centre, Noorwijk, Netherlands.

 

Announcement of first SPACEKIDs workshop

The first SPACEKIDS workshop has been announced.

Read more ...

SPACEKIDS Kicks-Off

The SPACEKIDS project "Kick-Off" meeting was held in Cardiff on  28th-29th January, 2013.

Read more ...
No events found