NDA General Ability Question (2025) — Solution

Step-by-step solution

In a telescope, the objective lens is designed to collect as much light as possible from distant objects to form a bright image. Therefore, it must have a large aperture. The magnifying power of a telescope in normal adjustment is given by M = f_o f_e , where f_o is the focal length of the objective and f_e is the focal length of the eyepiece. To achieve high magnification, the focal length of the objective lens must be much larger than that of the eyepiece. Thus, the objective lens has a larger focal length and a larger aperture compared to the eyepiece lens. Answer: larger focal length and larger aperture