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Old Dec 27th 2009, 09:29 PM   #1
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Light - Scale Drawing :(

Question - A converging lens is used to project an image of a slide onto a screen 1000mm from the lens, which has a focal length of 200mm. The image is a square with side 250mm. By means of a scale drawing, determine
a) the distance of the slide from the lens, and
b) the size of the slide.

I am stucked at this question... Wishing for a kind soul to show me the scale drawing which includes steps in drawing it Thanks in advance and sorry for the trouble..

Last edited by Punch; Dec 27th 2009 at 10:12 PM.
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Old Dec 27th 2009, 10:02 PM   #2
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a)250 mm ?
b) i thought the size of the image is already given. what do u think?
...............sorry. pleaseignore this. i did not see that scale drawing is required.

Last edited by r.samanta; Dec 27th 2009 at 10:04 PM. Reason: wrong post
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Old Dec 27th 2009, 10:13 PM   #3
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Originally Posted by r.samanta View Post
a)250 mm ?
b) i thought the size of the image is already given. what do u think?
...............sorry. pleaseignore this. i did not see that scale drawing is required.
Thanks, I realize that the question is, "the size of the SLIDE".
However, still unable to solve
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Old Dec 27th 2009, 10:33 PM   #4
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a)1/1000-1/(-u)=1/200 gives u=250 mm
b)m=v/u=I/O gives 1000/250=I/O=250/O gives O=62.5 mm.
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Old Dec 28th 2009, 12:31 AM   #5
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Originally Posted by r.samanta View Post
a)1/1000-1/(-u)=1/200 gives u=250 mm
b)m=v/u=I/O gives 1000/250=I/O=250/O gives O=62.5 mm.
lol guess i haven't been to your level yet, can u draw a scale drawing and show me how to derive the answer?sorry
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Old Dec 28th 2009, 05:53 AM   #6
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i am sorry but i really do not draw good in computers. i am way behind u on this.
however, what derivation are u asking?
i used lens formula 1/v-1/u=1/f and magnification=v/u =image size/object size,with sign conventions.
these must be derived in all standard textbooks?
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Old Dec 28th 2009, 07:01 PM   #7
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Originally Posted by r.samanta View Post
i am sorry but i really do not draw good in computers. i am way behind u on this.
however, what derivation are u asking?
i used lens formula 1/v-1/u=1/f and magnification=v/u =image size/object size,with sign conventions.
these must be derived in all standard textbooks?
well I haven't heard or learnt anything about lens formula and magnification formula yet.

regarding the scale drawing, perhaps u can draw it out on a rough paper and take a photo of it then upload it onto the photobucket.com and paste the link here.. it's okay if it isn't possible.. lol
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Old Dec 28th 2009, 07:29 PM   #8
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I figured how to draw already, thanks.
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