Problem 10.6. Two lenses are in contact, a converging one of focal length 30cm and a diverging one of focal length 10cm. What is the focal length and power of the combination?
Data
Focal length of first lens.f1 =30cm
Focal length of 2nd lens f2 = -10cm
To find
Focal length combination?
Power of combination?
Solution
Using the combination of lens formula 1/f =1/f1+1/f2
=1/30+1/-10. =1-3/30. =
1/f = 2/30 =-15cm answer 1
Power of lens is given by p= 1/f =1/ -15×10-²m. =100/-15. =-6.67 diopters
