onsdag 19 oktober 2011
Learning by Seeing
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.