PHYSICS QUESTION..PLEASE HELP!!!
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PHYSICS QUESTION..PLEASE HELP!!!

[From: ] [author: ] [Date: 11-05-26] [Hit: ]
..PLEASE!The focal length of a slide projecters converging lens is 10 cm. If a 35 mm slide is positioned 10.2 cm from the lens,......
I DONT GET THIS QUESTION WHATSOEVER.. PLS SPARE FROM YOUR TIME TO HELP THIS INNOCENT SOUL...PLEASE!


The focal length of a slide projecter's converging lens is 10 cm. If a 35 mm slide is positioned 10.2 cm from the lens, how far away must the screen be placed to create a clear image?




PLEASEEEE!

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The lens equation is 1/So + 1/Si = 1/f

where f = focal length, So = distance that the object is from the lens and Si = distance of the image from the lens. (See http://en.wikipedia.org/wiki/Optics for a detailed explanation and a diagram that will help you inderstand it better).

Solving the lens equation for Si:

1/Si = 1/f - 1/So = (So-f)/f*So

Si = f*So/(So-f)

Si = 10*10.2/(10.2 - 10) = 510cm

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s' = s*f/(s - f) = 10.2/(10.2 - 10) = 510 cm from the lens.
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