76. An astronomical refracting telescope will have large angular magnification and high angular resolution, when it has an objective lens of ?
(a) small focal length and large diameter
(b) large focal length and small diameter
(c) small focal length and small diameter
(d) large focal length and large diameter
Answer : (d) large focal length and large diameter
Concept / Approach: Telescopes have to capture as much light as possible to form a good image, so large diameter of objective lens (aperture) is preferred. Also for angular magnification $M_{\text{telescope}}=\frac{f_o}{f_e}$
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