Question:
In a reflecting telescope, a secondary mirror is used to:
In a reflecting telescope, a secondary mirror is used to:
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In a Cassegrain-type reflecting telescope the secondary mirror sends the light through a hole in the primary mirror so that the eyepiece can sit conveniently outside the tube.
Updated On: Nov 2, 2026
- make chromatic aberration zero
- remove spherical aberration
- reduce the problem of mechanical support
- move the eyepiece outside the telescopic tube
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The Correct Option is D
Solution and Explanation
In a reflecting (Cassegrain) telescope the large concave primary mirror collects light and reflects it toward a smaller secondary mirror.
The secondary mirror reflects this light back through a hole at the centre of the primary mirror, so the final image is formed behind the primary and the eyepiece can be placed outside the telescope tube, where it is easy to use.
Chromatic aberration is already absent in mirrors and spherical aberration is removed by using a parabolic primary mirror, not by the secondary mirror; the mechanical-support advantage comes from supporting the mirror from its back.
Answer: (4) move the eyepiece outside the telescopic tube
The secondary mirror reflects this light back through a hole at the centre of the primary mirror, so the final image is formed behind the primary and the eyepiece can be placed outside the telescope tube, where it is easy to use.
Chromatic aberration is already absent in mirrors and spherical aberration is removed by using a parabolic primary mirror, not by the secondary mirror; the mechanical-support advantage comes from supporting the mirror from its back.
Answer: (4) move the eyepiece outside the telescopic tube
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