A slide projector is used to display photographic slides onto a screen from the…
PHYSICS · Multi-part · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments
Problem
A slide projector is used to display photographic slides onto a screen 3.0m from the projector lens. Each slide has a height of 24mm and must appear 1.5m tall on the screen.
(a) Determine the required lateral magnification for the image on the screen.
(b) Assuming a single thin convex lens is used and that the slide is placed very close to the lens compared with the screen distance, calculate the object distance (slide–lens separation) needed to achieve the desired image height.
(c) Using the distances from part (b), determine the focal length of the projector lens.
(d) In practice the slide cannot be placed arbitrarily close to the lens because of mechanical constraints and heat from the lamp. If the minimum feasible slide–lens distance is 60mm, evaluate whether the design objective in part (a) can still be met with the focal length you calculated. If not, describe how the focal length or projector geometry would need to be modified.