Question

find the focal length and nature of lens which should be placed in contact with a lens of focal length 10 cm so that the power of combination becomes 5 dioptre ?​

Answer 1

Answer:

1 diopeter = 100/focal lenght (in cm)

Focal length = 1(1/a+1/a')

1/u + 1/v = 1/f.

f = 100/d (cm) P1 = 100/10 = 10 D. P2 = 100/f. focal length of two lenses in contact. f = f1f2/f1+f2. f = 1/d. power of 2 lenses in contact :-

P= P1 + P2.

if P2 is convex.

P= P1 - P2.

P1 = 100/f1.

I hope it helps you to understand.