Grade 11: Chapter 7: No 24

A telescope consists of two converging lenses. When in normal adjustment, so that the image of a distant object is formed at infinity, the lenses are 450 mm apart, and the magnifying power is 8. What are the focal lengths of the two lenses? Is the image erect or inverted?

Since the image is at infinity, MP = fo/fe = 8 fo = 8 fe L = fo + fe = 450 8 fe + fe = 450 fe = 50 mm and fo = 400 mm The final image is inverted.