Optical Instruments & the Eye
In a reflecting telescope, a secondary mirror is used to:
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Answer: (d)
- In a Cassegrain reflector, the concave primary mirror would form the image inside the tube, in the path of incoming light.
- The small convex secondary mirror reflects the converging beam back through a hole in the primary mirror.
- This brings the image, and so the eyepiece, outside the tube.
- So the answer is (d) move the eyepiece outside the telescopic tube.