Question

An astrnomical telescope having angular magnification 5 consists of two thin lenses 24cm apart. Find the power of it's lenses.​

Answer 1

given = magnifying power = 5

            2 thin lenses = 24 cm apart

            fο + fe = 24

           

to find = focal length.  

solution =   here we consider the fο and fe as a focal length

of objects.

fο + fe = 24cm       (.1)

M = fο / fe = 5

fο = 5 fe                    (2)

fe = 24cm / 6 = 4cm ___ from the above 2 equations

fο= 5fe = 5(4cm) = 20cm

the focal length of the lens​ is 20cm