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Question:

In an astronomical telescope in normal adjustment, a straight black line of length L is drawn on the inside part of the objective lens. The eyepiece forms a real image of this line. The length of this image is I. The magnification of the telescope is?

L+l/L-l

L/l+1

L/l

L/l

Solution:

Magnification of telescope: M = f₀/fₑ = -I/L

Therefore, f₀/fₑ = -I/L
Solving, we get f₀fₑ = LI = M