Comments on: I want one for our bath http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/ Just another WordPress blog Mon, 16 Jan 2012 20:39:32 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Bob http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/comment-page-1/#comment-96 Bob Mon, 31 Jul 2006 09:13:07 +0000 http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/#comment-96 If I've got it right, the anti-radar paint works in the same way as rainbows on soap bubbles. The radar wave hits the front surface of the paint and some bounces off (which normally would be detected in the normal way i.e. the plane shows up on radar). However, not all of it is reflected by the front surface and the rest carries on through to bounce off the back surface of the paint i.e. the paint / metal boundary. The clever bit is getting the paint just right, so that the two reflected bits match up in the right way so that they cancel each other out i.e. there's no reflection to go back to be detected. (A trough in one wave coincides with a peak in the other wave and vice versa, so they are each other's evil twin and cancel out.) This happens in soap bubbles too, but with light. The white light of sun light is a mixture of all the colours in the rainbow, and the difference in colour corresponds to a difference in the wavelength of the light. The reflection from the front surface and the reflection from the back surface cancelling each other out trick only works for one of the colours i.e. the one with a wavelength that fits with how thick the soap bubble wall is at that point. The wall of the soap bubble isn't the same thickness all over, so the colour that gets knocked out of the mix varies as you move around the surface of the bubble, which gives rise to the rainbow. Ain't physics great! If I’ve got it right, the anti-radar paint works in the same way as rainbows on soap bubbles. The radar wave hits the front surface of the paint and some bounces off (which normally would be detected in the normal way i.e. the plane shows up on radar). However, not all of it is reflected by the front surface and the rest carries on through to bounce off the back surface of the paint i.e. the paint / metal boundary. The clever bit is getting the paint just right, so that the two reflected bits match up in the right way so that they cancel each other out i.e. there’s no reflection to go back to be detected. (A trough in one wave coincides with a peak in the other wave and vice versa, so they are each other’s evil twin and cancel out.)

This happens in soap bubbles too, but with light. The white light of sun light is a mixture of all the colours in the rainbow, and the difference in colour corresponds to a difference in the wavelength of the light. The reflection from the front surface and the reflection from the back surface cancelling each other out trick only works for one of the colours i.e. the one with a wavelength that fits with how thick the soap bubble wall is at that point.

The wall of the soap bubble isn’t the same thickness all over, so the colour that gets knocked out of the mix varies as you move around the surface of the bubble, which gives rise to the rainbow. Ain’t physics great!

]]> By: Linda http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/comment-page-1/#comment-91 Linda Sat, 29 Jul 2006 15:16:59 +0000 http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/#comment-91 Well, you taught me something today as well. I didn't know about the special paint on stealth planes, always wondered how they avoided radar! Thanks ;-) Well, you taught me something today as well. I didn’t know about the special paint on stealth planes, always wondered how they avoided radar!

Thanks ;-)

]]> By: Nic http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/comment-page-1/#comment-90 Nic Fri, 28 Jul 2006 08:23:16 +0000 http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/#comment-90 That is very cool and reminds me of The Abyss! That is very cool and reminds me of The Abyss!

]]> By: Alison http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/comment-page-1/#comment-89 Alison Thu, 27 Jul 2006 22:53:15 +0000 http://www.inatthedeepend.org/2006/07/27/i-want-one-for-our-bath/#comment-89 Oh, that's so cool!!!!!! Oh, that’s so cool!!!!!!

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