Physics Help Forum diameter of the smallest image that lens creates

 Light and Optics Light and Optics Physics Help Forum

 Dec 7th 2009, 01:52 PM #1 Junior Member   Join Date: Dec 2009 Posts: 8 diameter of the smallest image that lens creates A point source of white light is located 3 meters from the lens in the previous problem, on its axis. The locations of the point images are at different places for different colors because of chromatic aberration so that the combined image is a circle. If the aperture of the lens has a diameter of 2 cm, what is the diameter of the smallest overall image of the point source that the lens creates? thank you
 Dec 30th 2009, 04:16 AM #2 Junior Member   Join Date: Dec 2009 Posts: 11 Hi, What level is this question? I would work out the angle the blue light is refracted, and then the same for red light, then use trig to work out what this ends up showing at 3 metres.
 Dec 30th 2009, 06:58 AM #3 Senior Member   Join Date: Sep 2009 Location: india Posts: 409 max, will i not need the focal lengths /refractive index for red and violet? otherwise how will i calculate the radius of the zone of least confusion?
 Dec 30th 2009, 07:47 AM #4 Junior Member   Join Date: Dec 2009 Posts: 11 I'm hoping that there is some info in the previous part of the question in which the lens is described. Sorry I havent heard of a zone of least confusion, we might just be using different terminology though. I've got some notes on chromatic aberation somewhere, i'll take a look.
 Dec 30th 2009, 08:13 AM #5 Senior Member   Join Date: Sep 2009 Location: india Posts: 409 i mean the region where the image has least diameter. i think its just a matter of terminology. if i know f red and f violet ,i will know the distance between the positions where the image has reddish rim and violet rim, and then use similarity relations to find the radius of the circle of least diameter between these two extremes? max,for your convenience, here is the link to the previous question, it doesnt have the info, though. http://www.physicshelpforum.com/phys...een-spots.html Last edited by r.samanta; Dec 30th 2009 at 08:28 AM.
 Dec 30th 2009, 08:35 AM #6 Junior Member   Join Date: Dec 2009 Posts: 11 I'd imagine that it will just be the diameter of the violet circle as it should all be symetrical and that will be the outermost. I am a little confused about it being in different places. alex 83, can you say what the previous part of the question is? Or even better upload the whole question? It's easier to work out if it's in context.Thanks,
 Dec 30th 2009, 08:42 AM #7 Senior Member   Join Date: Sep 2009 Location: india Posts: 409 Last edited by r.samanta; Dec 30th 2009 at 08:45 AM.
 Dec 30th 2009, 09:05 AM #8 Junior Member   Join Date: Dec 2009 Posts: 11 Thanks, I have to admit I havent seen that description before but it makes sense. I'm not sure if it is the same thing as the smallest image though, but rather the smallest image where the image is not distorted ie. all the pieces are in the right place. I think the smallest image will occur at the violet focal point and the size of the image will be that of the red circle. I could well be wrong though. Does the original question contain any of the focal lengths/refractive index information? Last edited by max; Dec 30th 2009 at 09:14 AM.

 Tags creates, diameter, image, lens, smallest

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post daniels77 Advanced Mechanics 4 Jun 23rd 2016 01:42 PM van-hilst Advanced Optics 2 Jan 31st 2015 05:57 AM rms390 Light and Optics 2 Sep 22nd 2010 09:07 AM Tap Water Advanced Optics 2 Apr 6th 2009 06:01 PM iamanoobatphysics Light and Optics 1 Dec 3rd 2008 08:27 AM