Modern telescopes prefer using concave mirror of large aperture as the objective instead of convex lens due to the following reasons:
(1) There is no chromatic aberration in a mirror.
(2) If the mirror is a parabolic mirror then even spherical aberration is also removed.
(3) Mechanical support of reflecting type telescope is easy to design and install because mirror weigh much less than a lens of equivalent optical quality.
Class 12 Physics
Chapter 9 Ray Optics and Optical Instruments Session 2024-2025.
Write three distinct advantages of a reflecting type telescope over a refracting type telescope.
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(i) No Chromatic Aberration: Reflecting telescopes avoid color distortions (chromatic aberration) since mirrors do not refract light.
(ii) Larger Apertures: Mirrors can be made much larger than lenses, allowing for more light gathering.
(iii) No Lens Sagging: Mirrors support their own weight, unlike lenses, which can sag and distort the image due to gravity.
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