Equivalent Focal Length of Lenses

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Equivalent Focal Length of Lenses

### Formula

$$\frac1F=\frac1{f_1}+\frac1{f_2}$$

### Terminologies

- F → Equivalent focal length.

- f1, f2 → Focal lengths of lenses.

### Conditions / Special Cases

For lenses in contact.

### Usage

- Used to find combined focal length.

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