Lens Maker's Formula

Rarely Tested

Lens Maker's Formula

### Formula

$$\frac1f=(\mu-1)\left(\frac1{R_1}-\frac1{R_2}\right)$$

### Terminologies

- f β†’ Focal length.

- ΞΌ β†’ Refractive index of lens material.

- R1, R2 β†’ Radii of curvature.

### Usage

- Used to calculate focal length of lens.

Question 1

A double convex lens made of glass of refractive index $$1.5$$ and radii of curvature of the curved surfaces $$20\,\mathrm{cm}$$ each is immersed in a liquid of refractive index $$n_L$$. The correct plot showing the variation of the power, in the units of diopter ($$D$$), as a function of $$n_L$$ is:

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