a) when a convex lens of focal lenght f is cut latitudinally.......... thenn focal lenth of each part is.....

b)when a convex lens of focal lenght f is cut longitudinally..............thenn focal lenth of each part is.....

PLS EXPLAIN WHY????

1/f=(U-1)(1/r₁-1/r₂)

a)f remains the same bcoz no change in radius of curvatures is there..its just intensity of light which changes resultin in decrese of brightness.

b)f changes becouse one of the radius of curvature changes(that is become infinity bcoz its now a plane surface).