Astronomical telescope refraction problem, an easy one

AI Thread Summary
An astronomical telescope is designed with an angular magnification of +5 and a total length of 16 cm, requiring calculations for the focal lengths of the objective and ocular lenses. The equations used include M = -(f_objective/f_ocular) and L = f_ocular + f_objective. The solution provided indicates f_ocular as -4 cm and f_objective as 20 cm, which raises questions about the nature of the lenses. However, the discussion clarifies that the telescope does not necessarily need to consist of two convergent lenses, validating the solution. The calculations appear correct despite initial concerns about lens types.
alpyurtsever
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Homework Statement



1.a) Design an astronomical telescope with an angular magnification of +5 (pay attention to + sign !) and
length of 16 cm, i.e. compute fobjective and focular).

Homework Equations



M=-(f_objective/f_ocular)
L=f_ocular+f_objective

The Attempt at a Solution



f_objective=16-f_ocular

M=-(16-f_ocular)/f_ocular

f_ocular = -4 cm
f_objective= 20 cm

I have found like that, but it says that it is an astronomical telescope in the question, where am I doing wrong. Astronomical telescope must consist of 2 convergent lenses, isn't it?
 
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alpyurtsever said:
Astronomical telescope must consist of 2 convergent lenses, isn't it?
No, not necessarily. Your solution looks good :smile:
 
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