Two lenses of power – 15 D and +15D are in contact with each other. The focal length of the combination is
A. + 10 cm
B. -20 cm
C. – 10 cm
D. + 20cm
Answer:C
Two lenses of power – 15 D and +15D are in contact with each other. The focal length of the combination is
A. + 10 cm B. -20 cm C. – 10 cm D. + 20cm