QJEEM19Phf86e: JEE Main 2019 Physics - Class 12 JEEM19Phf86e Solution: A plano convex lens of refractive index μ 1 and focal length ƒ…

Question

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A plano convex lens of refractive index

μ

₁ and focal length ƒ₁ is kept in contact with another plano concave lens of refractive index

μ

₂ and focal length ƒ₂. If the radius of curvature of their spherical faces is R each and ƒ₁ = 2ƒ₂, then

μ

₁ and

μ

₂ are related as -

Accepted Answer

\frac{1}{2 f_{2}} = \frac{1}{f_{1}} = (μ_{1} - 1) (\frac{1}{\infty} - \frac{1}{- R})

\frac{1}{f_{2}} = (μ_{2} - 1) (\frac{1}{- R} - \frac{1}{\infty})

\frac{(μ_{1} - 1)}{R} = \frac{(μ_{2} - 1)}{2 R}

2 μ_{1} - μ_{2} = 1

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