(a) (i) Draw a ray diagram of a reflecting telescope (Cassegrain) and explain the formation of image. State two important advantages that a reflecting telescope has over a refracting telescope. (ii) In a refracting telescope, the focal length of the objective is $50$ times the focal length of the eyepiece. When the final image is formed at infinity, the length of the tube is $102 \text{ cm}$. Find the focal lengths of the two lenses. OR (b) (i) Write any two advantages of a compound microscope over a simple microscope. Draw a ray diagram for the image formation at the near point by a compound microscope and explain it. (ii) A thin planoconcave lens with its curved face of radius of curvature $R$ is made of glass of refractive index $n_1$. It is placed coaxially in contact with a thin equiconvex lens of same radius of curvature of refractive index $n_2$. Obtain the power of the combination lens.