Question

Two convex lenses of focal lengths 0.3 m and 0.05 m are used to make a telescope. The distance kept between the two in order to obtain an image at infinity is :

• A. 0.35 m
• B. 0.25 m
• C. 0.175 m
• D. 0.15 m

Answer 1

Answer: (A)

0.35 m

In a telescope, to obtain an image at infinity or in normal adjustment, the distance between two convex lenses one called objective (greater focal length ) and the other called eye piece (shorter focal length ) is $L$.

$L=f_0+f_e=0.3+0.05=0.35m.$