lens combination power

Question

Equivalent power of two thin lenses in contact P1 and P2?

RankGuru · Accepted Answer

1. **Reciprocal Focal Lengths**: For two thin lenses of focal lengths $f_1$ and $f_2$ in contact, the equivalent focal length $F$ is given by $\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$.
2. **Linking to Power**: Since $P = 1/f$, we can directly substitute the power terms.
3. **Addition Rule**: The total power $P_{eq}$ is the algebraic sum of individual powers: **$P_{eq} = P_1 + P_2$**.
4. **Application**: This allows us to create combinations with desired convergence or divergence levels by simply adding lenses.
5. **Sign Note**: Converging lenses add positive values; diverging lenses add negative values.

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lens combination power

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