## In This post you will get answer of Q.

A point object is placed on the axis of a thin convex lens of focal length 0.05 m at a distance of 0.2 m from the lens and its image is formed on the axis. If the object is now made to oscillate along the axis with a small amplitude of A cm, then what is the amplitude of oscillation of the image? [you may assume,$frac{1}{1+x}approx1-x, where x

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Solution:

## $u=-0.2, f=0.05;frac{1}{v} =frac{1}{f}+frac{1}{u} =frac{100}{5}-frac{10}{2} =20-5 =15 or, v=frac{1}{15}m$

$frac{dv}{v^{2}}=-frac{du}{u^{2}} therefore dv=A.frac{v^{2}}{u^{2}}$

$A_{image} =Atimesfrac{1times25}{225times1} cm =frac{A}{9}cm or, A_{image} =frac{A}{9}times10^{-2}m$