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Photometry and Geometrical Optics

Problem 5.40

There are two thin symmetrical lenses: one is converging, with refractive index \(n_{1}=1.70,\) and the other is diverging with refractive index \(n_{2}=1.51 .\) Both lenses have the same curvature radius of their surfaces equal to \(R=10 \mathrm{~cm}\). The lenses were put close together and submerged into water. What is the focal length of this system in water?

Reveal Answer
f=n0R/2(n1−n2)=35 cm, where n0 is refractive index of waterf=n_{0} R / 2\left(n_{1}-n_{2}\right)=35 \mathrm{~cm}, \text { where } n_{0} \text { is refractive index of water}
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