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May 11th, 2011, 02:53 AM   #1
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Converging lens & convex mirror

The focal length of the converging lens is d and the object distance to the converging lens is 2d. The convex mirror is distance d behind the lens and the magnitude of it's focal length is 2d.

Find the final image distance.

I've been going over this problem for hours and even using simulations and I have two problems with it:
1)The focal lengths and their spacing makes it so it appears as though images disappear (sometimes in the simulation it seems like they vanish inside the lens).
2)I'm not sure what exactly the final image is supposed to be. The simulations show 3-4 "images".

I've gotten the first part which is 1/d = 1/2d + 1/i --> i = 2d (M = -1 so it's inverted and the same size on the left side of the convex mirror.
Attempt at part 2) f=-2d for the convex mirror and the image is distance d behind it.
-1/2d = -1/d + 1/i --> i = 2d (M2 = -2d/-d = 2, M1*M2 = (-1)(2) = -2 so the image is inverted and twice the size of the original.)

That seems like the solution, but again, any simulation seems really funky with the proportions involved. That and from doing the simpler counterparts to problems like this it would seem like I would need to make a third image calculation using the lens again but that's where the simulation screws up and the formula shows 0=1/i (which is why I'm guessing the image disappears at certain points).

Any advice would be appreciated.
Mnimetic is offline  
May 24th, 2011, 06:54 AM   #2
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Re: Converging lens & convex mirror

Have you tried paper and pencil (draw a ray diagram)?
MRWhy is offline  
June 4th, 2011, 06:10 PM   #3
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See this.
johnny is offline  
October 14th, 2013, 11:36 PM   #4
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Re: Converging lens & convex mirror

It is learned earlier that a convex mirror diverges light, as does a concave lens. How to recognize a convex lens is t is thicker in the center than the ends, but a concave lens is thicker at the ends than in the center. That is their major difference to distinguish them.

Stop snoring -
BlueLotus is offline  

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