What Focal Length is Needed to Project a 35mm Slide onto a Large Screen?

AI Thread Summary
To project a 35mm slide onto a large screen measuring 1.80m by 2.70m from a distance of 7.50m, the appropriate focal length of the lens must be calculated. The lens equation (1/Do) + (1/Di) = 1/f is essential for this calculation, where Do is the object distance and Di is the image distance. Additionally, the magnification formula is necessary to determine how much the image needs to be enlarged to fit the screen dimensions. The discussion highlights the need for clarity on these equations to solve the problem effectively. Understanding both the lens and magnification equations is crucial for finding the correct focal length.
scottatkins
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Homework Statement


A 35mm slide(picture size is actually 24 by 36 mm)is to be projected on a screen1.80m by 2.70 m placed 7.50m from the projector. What focal length lens should be used if the image is to cover the screen?

Homework Equations



the only equation i can think of is the lens equation which is (1/Do)+(1/Di)=1/f

The Attempt at a Solution


I have tried starting this problem numerous times and just have no clue how to start it
 
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You need the formula for magnification, too.

ehild
 

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