PHYSICS HELP NEEDED! optics?

Question

A slide projector has a converging lens whose focal length is 105 mm.

(a) How far (IN METERS) from the lens must the screen be located if a slide is place 108 mm from the lens.?

(b) If the slide measures 24.0 mm x 36.0 mm , what are the dimensions ( in mm) of its image?

Answer 1

use the standard lens equation to give an image distance of

3780mm or 3.78 m

Then magnification = image distance/object distance = 35

so the image will be 35 times 24.0 mm by 36.0 mm