When someone mentions infrared, the first thing that generally comes to mind is the old heat lamp you use to help hatch chickens or to convince your friends that you've spent the winter in Florida. The energy from that lamp covers a large part of the infrared portion of the electromagnetic spectrum.

Infrared starts where visible leaves off: in the EM spectrum, red grades into reflective infrared. This is the infrared energy reflected from the surface of the object.

The light from that old infrared heat lamp looked red, didn't it? Were we seeing infrared light? No, what we actually saw was the red end of the visible spectrum, but we did feel the infrared energy. Our eyes cannot see infrared. The heat we sensed was the other end of the infrared spectrum.

The infrared portion of the spectrum is one of the most useful for identifying what a surface is made of because there is both reflected energy and emitted energy. Plants reflect much more energy in the reflected infrared than in the visible, and we can determine the state of the health of the plant from its reflectance. The reflected infrared energy also tells us a lot about rocks and minerals that may be present. For example, we can often distinguish clay-bearing minerals from other minerals (important in gold and silver exploration), although it usually takes additional information to classify specific rocks.

[Index]