A lens made of material of Refractive index - 2 is surrounded by a medium of Refractive Index - 1- The focal length f is related as -

The correct option is B f∝ 1 ( μ _ 2 μ_ 1 ) From lens maker's formula : 1 f =( μ #160; _ 2 μ #160; _ 1 μ #160; _ 1 #160; ) [ 1 R _ 1 ...

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Standard XII

Physics

Lens Maker's Formula

A lens made o...

Question

A lens made of material of Refractive index $μ_{2}$ is surrounded by a medium of Refractive Index $μ_{1}$ . The focal length f is related as :

f \propto (1 - μ_{2} - μ_{1})

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f \propto \frac{1}{(μ_{2} - μ_{1})}

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f \propto \frac{1}{(μ_{2} + μ_{1})}

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f \propto \frac{1}{(μ_{2} + μ_{1})}

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Solution

The correct option is B $f \propto \frac{1}{(μ_{2} - μ_{1})}$
From lens maker's formula :

$\frac{1}{f} = (\frac{μ_{2} - μ_{1}}{μ_{1}}) [\frac{1}{R_{1}} - \frac{1}{R_{2}}]$

$f \propto \frac{1}{μ_{2} - μ_{1}}$

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Similar questions

Q. A double convex lens, lens made of a material of refractive index

μ_{1}

is placed inside two liquids or refractive indices

μ_{2}

and

μ_{3}

, as shown

μ_{2} > μ_{1} > μ_{3}

. A wide, parallel beam of light is incident on the lens from the left.

What is the relation between refractive indices $μ_{1}, μ_{2} and μ_{3}$ if the behaviour of light rays is as shown in the figure. The refractive index of medium to the left of the lens is $μ_{1}$ , that of lens is $μ_{3}$ and that of medium to the right of lens is $μ_{2}$ .

Q. A right angled prism of refractive index

μ_{1}

is placed in a rectangular block of refractive index

μ_{2}

, which is surrounded by a medium of refractive index

μ_{3},

as shown in the figure. A ray of light

^{'} e^{'}

enters the rectangular block at normal incidence. Depending upon the relationship between

μ_{1}, μ_{2}

and

μ_{3},

it takes one of the four possible paths

^{'} e f^{'},^{'} e g^{'},^{'} e h^{'}

^{'} e i^{'}

Match the paths in

List -I

with conditions of refractive indices in

List -II

and choose the correct answer.
List - I List - II

$(P) e \to f$	$(1) μ_{1} > \sqrt{2} μ_{2}$
$(Q) e \to g$	$(2) μ_{2} > μ_{1} & μ_{2} > μ_{3}$
$(R) e \to h$	$(3) μ_{1} = μ_{2} = μ_{3}$
$(S) e \to i$	$(4) μ_{2} < μ_{1} < \sqrt{2} μ_{2} & μ_{2} > μ_{1}$

An equi convex lens is made of a material of refractive index $μ_{1}$ and is placed inside two liquids of refractive indices $μ_{2}$ and $μ_{3}$ as shown with $μ_{2} > μ_{1} > μ_{3}$ . A wide, parallel beam of light is incident on the lens from the left. The lens will give rise to: