In a Cassegrain-type reflecting telescope

PHYSICS · Single correct · CBSE · Physics · Ray Optics and Optical Instruments · Ray Optics and Optical Instruments

Problem

In a Cassegrain-type reflecting telescope, the concave primary mirror has a focal length of

120\,\text{cm}

. A convex secondary mirror increases the effective focal length of the system to

360\,\text{cm}

. If an eyepiece of focal length

4\,\text{cm}

is used, calculate the magnifying power of the telescope under normal adjustment. (a)

60

(b)

90

(c)

30

(d)

120