Match List-I with List-II.
| List-I (Feature of a telescope) | List-II (What it gives) |
|---|---|
| (A) A pair of inverting lenses in a terrestrial telescope | (I) Fainter objects can be seen |
| (B) A concave mirror as the objective | (II) A large focal length in a short tube |
| (C) A convex secondary mirror, as in the Cassegrain telescope | (III) The final image is erect |
| (D) An objective of large diameter | (IV) No chromatic aberration in the objective |
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (A)-(III), (B)-(IV), (C)-(II), (D)-(I)
(A) A pair of inverting lenses in a terrestrial telescope — This matches (III). An astronomical telescope gives an inverted image. The extra pair of lenses turns it upright for viewing objects on the earth.
(B) A concave mirror as the objective — This matches (IV). A mirror forms the image by reflection alone. So there is no chromatic aberration in a mirror objective.
(C) A convex secondary mirror, as in the Cassegrain telescope — This matches (II). The convex mirror sends the light back through a hole in the main mirror. The light path folds, so a long focal length fits in a short tube.
(D) An objective of large diameter — This matches (I). A larger objective collects more light, so fainter objects can be seen.
NCERT (2026-27):
Telescope – “Terrestrial telescopes have, in addition, a pair of inverting lenses to make the final image erect. …”
Telescope – “… Telescopes with mirror objectives are called reflecting telescopes. There is no chromatic aberration in a mirror. …”
Telescope – “… This is known as a Cassegrain telescope, after its inventor. It has the advantages of a large focal length in a short telescope. …”
Telescope – “… The former clearly depends on the area of the objective. With larger diameters, fainter objects can be observed. …”