A convex lens of focal length f1 and a concave lens of focal length f2 are placed in contact. The focal length of the combination is

A convex lens of focal length f1 and a concave lens of focal length f2

1.	A convex lens of focal length f1 and a concave lens of focal length f2 are placed in contact. The focal length of the combination is
A.	F2 + f1
B.	F2 - f1
C.	F1f2/f2+f1
D.	F1f2/f1-f2
Answer» E.