onsdag 19 oktober 2011

Learning by Seeing

Simplified optical setup used in thermal detection

Everyday you may learn something new. I just discovered that I made a mistake in the recent post on IR-detectors believing that an optical lens may increase the radiance from a target onto a detector, because a (positive) lens increases the amplitude of the incoming light waves by making the rays converge.

But then I missed that the viewing angle also increases which makes the radiance the same after the lens as before. This means that the detector even with an optical lens cannot reach a higher temperature than the target, in full accordance with the 2nd law.

1 kommentar:

  1. You beat me to, I were about to ask where you find the battery holder on Kepplers old telescope?