The magnifying power of an astronomical telescope can be

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The magnifying power of an astronomical telescope can be decreased by

1. decreasing the focal length of the eyepiece
2. increasing the focal length of the eyepiece
3. increasing the focal length of the objective
4. None of these

Correct Option: B

The magnifying power (M) of astronomical telescope
is given by M = focal length of objective focal length of eye piece . This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.