Question

Hey guys help me with this one ​

Answer 1

Reflective index quantity indicates the degree of convergence or divergence of a light ray passing through the lens.

focal length +75 of a lens tells that it is convex lens as its focal length is in plus......its power ,p=1/f(focal length)

p=1/+75

=+0.0133 dioptres......

the minus sign of another focal length tells that it is concave lens.....its power,p=1/f

p=1/-75

=-0.0133 dioptres.