A astronomical telescope has objective and eyepiece of focal length 40 cm and 4 cm respectively. To view an object 200 cm away from the objective, the lenses must be separated by a distance

Options

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

Answer

B, C, D

Explanation

Here, object is at 200 cm away, hence if the image distance of objective is `v_0delta`, then
`(1)/(f_0)=(1)/(v_0)-(1)/(u_0)`
`therefore (1)/(v_0)=(1)/(f_0)+(1)/(u_0)`
`=(1)/(40)+(1)/(-200)`
`=(5-1)/(200)=(4)/(200)=(1)/(50)`
`therefore v_0=50` cm
Here,tube length L=`v_0+f_e`
=50+4=54 cm