Why is it beneficial to use a parabolic mirror instead of an objective convex lens in a telescope?
Choose the most correct answer.

Correct option is C

The correct answer is (c) Parabolic mirror does not have color astigmatism and spherical aberration compared to a convex lens, and the mirror is lighter than a convex lens.

Advantages of Using a Parabolic Mirror in Telescopes:

1. No Chromatic Aberration:

   • Mirrors, unlike convex lenses, do not refract light.
   • This eliminates chromatic aberration, a phenomenon where different wavelengths of light (colors) focus at different points, causing distortions in the image.

2. No Spherical Aberration:

   • Parabolic mirrors ensure all incoming parallel rays converge at the same focal point.
   • This avoids spherical aberration, a flaw that occurs when spherical lenses or mirrors fail to focus all rays at the same point.

3. Lightweight Design:

   • Mirrors are typically lighter than lenses of equivalent size.
   • They can be thinner and supported from behind, making them more practical for large telescopes.

Thus, parabolic mirrors eliminate chromatic aberration and spherical aberration while being lightweight, making them ideal for telescopes.

Additional Information:

Telescope Overview:

• A telescope is an optical instrument designed to observe distant objects by collecting and magnifying light.
• Widely used in astronomy to study celestial objects like stars, planets, and galaxies.

Types of Telescopes:

1. Refracting Telescope:

   • Uses lenses to bend (refract) light to form an image.
   • Example: Galileo’s telescope.
   • Limitation: Suffers from chromatic aberration.

2. Reflecting Telescope:

   • Uses mirrors to reflect light and form an image.
   • Example: Newtonian telescope.
   • Advantage: No chromatic aberration, lighter design.

3. Catadioptric Telescope:

   • Combines lenses and mirrors for improved image quality.

Key Components of a Telescope:

• Objective (Lens/Mirror): Collects light from distant objects.
• Eyepiece: Magnifies the image for viewing.
• Mount: Provides stability and allows smooth movement for tracking objects.