Question

an astronomical telescope having magnifying power of 5 consists of two thin lenses 24 cm apart .find the focal length of the lens​

Answer 1

Answer:

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 lenth

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