Question

A thin convex lens of focal length 20 cm is
placed in closed contact with a thin concave
lens of focal length 5 cm. The power of
combination is​

Answer 1

Answer:

5D

Explanation:

Focal of convex lens(f)=+20cm=20/100=+.20m

44P=1/f=1/.20=100/20=+5D$$

focal length of concave lens(f)=−10cm=−10/100=−.1m

P=1/−.1=−10D

power of combination=5−10=−5D