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Geometrical Optics

Section: Physics

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Question : 26 of 59

Marks: +1, -0

A wire is bent in the shape of a right angled triangle and is placed in front of a concave mirror of focal length f, as shown in the figure. Which of the figures shown in the four options qualitatively represent(s) the shape of the image of the bent wire? (These figures are not to scale.)

[JEE Adv 2018 P2]

Solution:

distance of a point A is

\frac{f}{2}

Let A’ is the image of A from mirror, for this image

\frac{1}{v}+\frac{1}{-\frac{f}{2}}=\frac{1}{-f}\qquad\frac{1}{v}=\frac{2}{f}-\frac{1}{f}=\frac{1}{f}

Image of line AB should be perpendicular to the principle axis & image of F will form at infinity, therefore correct image diagram is

\frac{f}{f-u}=\frac{h_2}{h_1}\qquad h_2=\frac{-f(f-x)}{-f+x}h_2=f

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