what is the meaning of focal lengths on both the sides of lens

Dear student

 

Light can pass through a lens from either dierction or side. therefore, a lens has two principal foci which are situated at equal distances from the optical centre, one on either side of the lens. These equal distances are refered to as focal lengths, hence a lens has two focal lengths on its both the sides.

 

The distance from the optical centre of the lens to its first focal point is called first focal length and the distance from the optical centre of the lens to its second focal point is called second focal length.

 

We hope this clarifies your doubt.

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