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. The objective lens in a refracting telescope has a larger aperture to collect more light from distant objects, enhancing brightness and resolution. The eyepiece, with a smaller aperture, magnifies this image, requiring less light-gathering capacity for viewing. Substituting values gives To gather more light for brightness, which