Practice question

**Simple microscope** magnification M = 1 + D/f when image at D=25 cm near point, M = D/f when image at infinity (relaxed eye), f focal length (cm), D least distance of distinct vision 25 cm. For f=4 cm, image at 25 cm, M=1+25/4=7.25, angular magnification ratio of angle subtended by image to that by object at D. In a reflecting telescope (e.g., Cassegrain design), a secondary mirror redirects the light focused by the primary concave mirror through a hole in the primary mirror to the eyepiece. This allows a compact design with a long focal length, improving magnification and convenience of observation. Substituting values