Two thin lenses, one of focal length + 60 cm and the other of focal length – 20 cm are put in contact, the combined focal length is,
A. 15 cm
B. – 15 cm
C. – 30 cm
D. 30 cm
Answer:C
Two thin lenses, one of focal length + 60 cm and the other of focal length – 20 cm are put in contact, the combined focal length is,
A. 15 cm B. – 15 cm C. – 30 cm D. 30 cm