Question

First focal length of the convex lens
__cm

Answer 1

For convex lens the focal length is positive. On the other hand, thefocal length of concave lens is negative. Thus, for convex lens, thefocal length is a distance over which all the parallel rays will converge. A certain point over thatdistance all the parallel rays will converge, that point is known asfocal point.

Answer 2

➡The reciprocal of the focal length, 1/f, is the optical power of the lens. Of the focal length is in metre, this gives the optical power I'm dioptres. Lenses have the same focal length when light travels from the back to the front as when light goes from the front to the back.⬅

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