Question

a thin convex lens of focal length 10cm is placed in contact with a concave lens of same material and same focal length. the focal length of the combination is?

Answer 1

f1=+10cm

f2 = -10cm

P= 1/f1 + 1/f2

P= 100/ 10 + 100/ -10

P = 10m - 10m

P = 0