An astronomical telesope has objective and eyepiece of focal lengths `40cm` and `4 cm` respectively. To view an object `200cm` away from the objective, the lenses must be separated by a distance `:`

Options

A. 37.3 cm
B. 46.0 cm
C. 50.0 cm
D. 54.0 cm

Answer

D

Explanation

`f_(o) = 40 cm , f_(e) = 4 ` cm
`u_(o) = - 200 `cm
`(1)/(v_(0)) = (1)/(f_(o)) + (1)/(u_(o)) = (1)/(40) - (1)/(200) rArr v_(o) = 50` cm
Tube length = I =`v_(o) + f_(e) = 54 ` cm .