Question

what is the focal length of the lens if it's power is 7D​

Answer 1

Answer:

1. ) Two thin lenses of power +7D & -3D are in contact. · The plano-convex lens of focal length 20cm and 30cm are placed together to form a ...

Answer 2

Answer:

two thin lenses of power +7D and -3D are in contact with is the focal length of the combination