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How can I find the net focal length when two lenses of different materials are in contact? Also the set of lenses are surrounded by air.Please provide help on basis of the attached image.

How can I find the net focal length when two lenses of different materials are in contact? Also the set of lenses are surrounded by air.Please provide help on basis of the attached image.

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Grade:11

1 Answers

ADARSH SINGH
123 Points
5 years ago
DEAR FRIEND,

IF YOU KNOW THE FOCAL LENGTHS OF TWO DIFFRENT LENSES IN CONTACT, THEN YOU ARE ASKING HOW TO KNOW THE NET FOCAL LENGTH . RIGHT?
SO,
HERE IS THE DIRECT FORMULA FOR THE SAME.
LET F1 BE THE FOCAL LENGTH OF  FIRST LENS AND F2 BE THE FOCAL LENGTH OF SECOND LENS. ALSO , LET  Fx BE THE NET FOCAL LENGTH OF THE LENSES WHEN THEY ARE IN VERY CLOSE CONTACT.
THEN,
1/Fx = 1/F1 + 1/F2

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