Question

a convex length of focal length 10 cm is placed in closed contact with a concave lense of focal length 10 cm the power of combination​

Answer 1

Given,

f 1 =+10cm for convex lens

f 2 =−20cm for concave lens

The focal length of the combination is given by f

1 = f 2

1 + f 2

1 f

1 = +10cm

1 + −20cm

1 = 20cm

1 f=+20cm

hope it helps

have a great day dear