The value of the focal length of the lens is equal to the value of the image distance when the rays are
A. passing through the optic centre
B. parallel to the principal axis
C. passing through the focus
D. in all the cases
Answer:D
The value of the focal length of the lens is equal to the value of the image distance when the rays are
A. passing through the optic centre B. parallel to the principal axis C. passing through the focus D. in all the cases