26-9 You have two lenses with focal lengths f 1 = +37.5 cm and f 2 = +5.5 cm tha

Question

26-9

You have two lenses with focal lengths f1 = +37.5 cm and f2 = +5.5 cm that you can mount on either end of a telescope barrel with an adjustable length. Determine the following.

(a) the lens you should use for the objective of the telescope

(b) the distance needed between the lenses in order for the telescope to focus on an infinitely distant object and produce an infinitely distant image


(C) the distance needed between the lenses in order for the telescope to focus on an object that is 6.00 m away and to produce an infinitely distant image

Explanation / Answer

a) Lens used for objective has higher focal length, so f1=37.5cm is taken.

b) f1+f2 = 37.5+5.5 = 43cms

c) 1/f-1/obj = 1/img

1/37.5 -1/600 = 1/x

0.026-0.0016= 1/x

x=40 cm

1/5.5 -1/x = 1/40

0.181 -1/x = 0.025

1/x = 0.156

x=6.4cm

distance between lenses = 43 + 6.4 = 49.4cms

Related Questions

Navigate

• Browse (All)
• Browse 2
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.