Question:
Write two advantages of reflecting telescope over refracting telescope.
Write two advantages of reflecting telescope over refracting telescope.
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Paraboloidal mirrors are preferred in reflecting telescopes over spherical mirrors to eliminate spherical aberration completely without needing corrective lenses.
Updated On: Sep 14, 2026
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Solution and Explanation
Concept:
• Objective lens collects light from faint, distant astronomical bodies.
• Light gathering power is proportional to area of aperture ($\propto D^2$).
• Resolving power is given by $R.P. = \frac{D}{1.22 \lambda}$.
Step 1: Advantages of Reflecting Telescope over Refracting Telescope
1. Absence of Chromatic Aberration: Reflecting telescopes use parabolic mirrors instead of lenses. Since reflection does not depend on wavelength, images are completely free from chromatic aberration.
2. High Light Efficiency and Easy Support: Large parabolic mirrors can be supported along their entire back surface rather than just at edges (unlike heavy thick lenses), avoiding mechanical sagging. Also, mirrors require surface polishing only, making them cheaper and lighter to fabricate with huge diameters.
Step 2: Conclusion
Large objective aperture maximizes light collection and spatial resolution. Reflecting telescopes overcome chromatic aberration and structural weight constraints inherent to refracting lens systems.
• Objective lens collects light from faint, distant astronomical bodies.
• Light gathering power is proportional to area of aperture ($\propto D^2$).
• Resolving power is given by $R.P. = \frac{D}{1.22 \lambda}$.
Step 1: Advantages of Reflecting Telescope over Refracting Telescope
1. Absence of Chromatic Aberration: Reflecting telescopes use parabolic mirrors instead of lenses. Since reflection does not depend on wavelength, images are completely free from chromatic aberration.
2. High Light Efficiency and Easy Support: Large parabolic mirrors can be supported along their entire back surface rather than just at edges (unlike heavy thick lenses), avoiding mechanical sagging. Also, mirrors require surface polishing only, making them cheaper and lighter to fabricate with huge diameters.
Step 2: Conclusion
Large objective aperture maximizes light collection and spatial resolution. Reflecting telescopes overcome chromatic aberration and structural weight constraints inherent to refracting lens systems.
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