Help Solve Lens Projector Distance Puzzle!

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Homework Help Overview

The discussion revolves around a problem involving a converging lens used in a slide projector, specifically focusing on determining the distance between the lens and the transparency when projecting an image onto a screen 10 meters away. The focal length of the lens is given as 25 cm.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply the lens formula to find the distance from the lens to the transparency but expresses uncertainty about their calculation. Some participants question the validity of the original poster's result and suggest alternative values, indicating confusion about the setup.

Discussion Status

The discussion is ongoing, with participants sharing their interpretations and calculations. Some guidance has been offered, but there is no clear consensus on the correct approach or result at this time.

Contextual Notes

Participants are grappling with the conversion of units and the implications of the distances involved, as well as the source of alternative values mentioned in the discussion.

cuddlylover
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I have this in my home work and i am not 100% on if i have it right or not

A converging lens with a focal length of 25 cm is used to make a slide projector. If the image is to be projected onto a screen 10m away, how far should the lens be located from the transparency?

I did it like this:

1/s + 1/1000cm = 1/25cm

solve for s

1/s = 1/25cm - 1/1000cm
∴ s = 25.64cm (2dp)

Is this right or am i way off. If some one could help would be a big help thanks.
 
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Or should it be 3.9mm i am a bit lost here i think lol.
 
Looks OK to me.
 
cuddlylover said:
Or should it be 3.9mm i am a bit lost here i think lol.
Where did you get that value?
 
I posted this somewhere else and someone posted that but could not see how they got to it :)
 

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