A biconvex lens of focal length $f$ and radii of curvature of both the surfaces $R$ is made of a material of refractive index $n_{1}$ . This lens is placed in a liquid of refractive index $n_{2}$ . Now this lens will behave like:

either as convex or as a concave lens depending solely on

R

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a convex lends depending on

n_{1}

and

n_{2}

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a concave lends depending on

n_{1}

and

n_{2}

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a convex lens of same focal length irrespective of

R, n_{1}

and

n_{2}

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Solution

The correct options are
A a convex lends depending on $n_{1}$ and $n_{2}$
C a concave lends depending on $n_{1}$ and $n_{2}$
The convex lens will be converging, i.e., will behave like a convex lens when $n_{1} > n_{2}$ .
The same convex lens will be diverging, i.e., will behave like a concave lens when $n_{1} < n_{2}$
So, the convex lens will behave like a convex or a concave lens depending on the values of $n_{1}$ and $n_{2}$ .

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Similar questions

Q. A concave lens made of a material of refractive index

n_{1}

is kept in a medium of refractive index

n_{2}

. A parallel beam of light is incident on the lens. Complete the path of rays of light emerging from the concave lens if:
(a)

n_{1} > n_{2}

and (b)

n_{1} < n_{2}

.
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Q. A convex lens made of material of refractive index n 2 is kept in a medium of refractive index n1. A parallel beam of light is incident on the lens. Compare the path of rays of light emerging from the convex lens if (i) n1 < n2 (ii) n1 = n2 (iii) n1 > 1.

A thin convex lens is made of two materials with refractive indices $n_{1}$ and $n_{2}$ , as shown in figure. The radius of curvature of the left and right spherical surfaces are equal. $f$ is the focal length of the lens when $n_{1} = n_{2} = n$ . The focal length is $f + Δ f$ when $n_{1} = n$ and $n_{2} = n + Δ n$ . Assuming $Δ n << (n - 1)$ and $(1 < n < 2)$ , the correct statement(s) is/are: