A convex lens of 40 cm focal length is combined with a concave lens of focal length 25 cm. The power of combination is
A. -1.5 D
B. – 6.5 D
C. + 6.6 D
D. + 6.5 D
Answer:A
A convex lens of 40 cm focal length is combined with a concave lens of focal length 25 cm. The power of combination is
A. -1.5 D B. – 6.5 D C. + 6.6 D D. + 6.5 D