Physics Help Forum Lens on filament?

 Light and Optics Light and Optics Physics Help Forum

 Sep 6th 2009, 09:44 PM #1 Member   Join Date: Jul 2009 Posts: 86 Lens on filament? A diverging lens with focus 5 cm is placed in a filament. Find the distance between the lens and the filament. I use formula : $\displaystyle \frac{1}{f}=\frac{1}{di}+\frac{1}{do}$ I think the question is asking about do = distance of the object. But I don't know di (distance of image). How to solve this problem? Thanks
 Sep 7th 2009, 10:15 PM #2 Physics Team   Join Date: Feb 2009 Posts: 1,425 Please check your question again. If the lens is in the filament, how can there be a distance between them?
 Sep 8th 2009, 04:50 AM #3 Member   Join Date: Jul 2009 Posts: 86 Hi physicsquest The original question is "A diverging lens with focus 5 cm is placed on a filament. Find the distance between the lens and the filament." But it also can be interpreted that there is no distance between the filament and the lens. So I think maybe the lens is placed in a bulb with a distance from the bulb filament. But I'm not sure. Thanks

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