Question

Two thin lenses of focal length 20cm and -15cm are kept in contact. What is the focal length and power of the combination

Answer 1

Hey mate

Here goes your answer

I/f of 1st lens =1/0.2 =5 D

I/f of 2nd lens =1/-0.15 = -6.667 D

Total focal length = 20-15=5 cm = 00.5 m

Total power = -1.666... D