why focal length of convex lens is taken as positive

Asked by ammulusri97 | 29th Apr, 2020, 11:30: AM

Expert Answer:

Convex lens always converges the light rays incident on it to the focal point which to the right side of the convex lens. 
According to the New Cartesian sign convention, all distances measured to the right of the origin (along +x-axis) are taken as positive, while those measured to the left of the origin (along −x-axis) are taken as negative.
Hence, Focal length of convex lens is positive.

Answered by Shiwani Sawant | 29th Apr, 2020, 01:32: PM