Question

The power of two lense are in the ratio 4:1 , what would be the ratio of focal length of these lens ?​

Answer 1

ANSWER

For an achromatic combination, 

w1f1+w2f2=0

Also, the effective focal length of the combination will be:

f1=f11+f21

Solving these simultaneously and substituting the values, the obtained focal lengths are, fo=15 and fe=−20

Answer 2

Answer:

1/4 ।...

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.

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ok because

power =1/f

power second.=1/f2