A Cassegrain telescope has a hole in the main mirror. This reduces the mirror area and thus the light gathering power, but how much? Suppose a ten inch diameter mirror has a one inch diameter hole in the center. How much of the light gathering power is lost because of the hole?

1%

Explanation: A cassegrain telescope is a kind of telescope which is made up of the curved mirrors one of the mirrors is a concave mirror is called the primary mirror and the second mirror called the secondary mirror which is a convex mirror, when light Penetrate the cassegrain telescope, it first hits the primary concave mirror and it's then reflected by the secondary convex mirror.

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