Question

The optical length of an astronomical telescope with magnifying power of ten for normal vision is 44 cm. what is the focal length of the object

Options

• 440 cm

• 49 cm

• 40 cm

• 4 cm

Answer 1

40 cm

Explanation:

m = `(fo)/(fe)` = 10

fo = 10 fe

L = fo + fe on 44 = 10fe + fe = 11fe

fe = 4 cm

fo = 10fe = 10 × 4 = 40 cm