Question

two focal lengths are in contact a converging of focal length 30 cm and a diverging one of focal length -10cm. What is the focal length of the combination?

Answer 1

Answer:

focal length of each two concave lense = -30

the effective focal length formula given by

1/ f = 1/F1 + 1/F2

F1 = -30

F2 = -30

1/f = -1 / 30 - 1/30

1/f = -1/15

the focal length of the compound lens -15 cm

Answer 2

Explanation:

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