A camera lens of focal length 35.0 mm photographs a flower 75.0 cm away. How far from the lens must the film sit for a sharp image?

1. Work in one unit throughout: 75.0 cm = 750 mm, so do = 750 mm and f = 35.0 mm, both positive for a converging lens. 2. Use the rearranged thin lens equation di = f do divided by (do minus f). 3. Substituting with units, di = (35.0 mm times 750 mm) divided by (750 mm minus 35.0 mm). 4. The numerator is 26250 mm squared and the denominator is 715 mm. 5. So di = 36.7 mm, and the positive value confirms a real image that the film can record. 6. The image distance is a little larger than the focal length, as it must be for any object beyond the focal point. 7. Answering 35.0 mm treats the flower as infinitely far away, which is only valid for very distant subjects. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.6 Image Formation by Lenses_