A 35 mm film is to be projected on a 20 m wide screen situated at a distance of 40 m from the filmprojector. Calculate the distance of the film from the projection lens and focal length of projection lens.

Explanation

To solve the problem, we need to determine two things: the distance of the film from the projection lens (object distance, U) and the focal length of the projection lens (f). We will use the lens formula and the magnification formula for this purpose.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Height of the film (object height, O) = 35 mm = 35 × 10^(-3) m = 0.035 m
- Width of the screen (image height, I) = 20 m
- Distance from the projector to the screen (image distance, V) = 40 m
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