An object is placed 20 cm to the left of a convex lens of focal length 10 cm. If a concave mirror of focal length 5 cm is placed 30 cm to the right of the lens, find the magnification.

1.5

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Solution

The correct option is B $1$
AC = Object distance = 20 cm

BC = focal length of the lens = 10 cm

So, object is placed at the centre of curvature of the lens.

So, CD = Image distance = 20 cm

Magnification $m_{1} = 1$

Now DF = 10 cm.

EF = focal length of the mirror = 5 cm

So, image form the lens will be at the centre of curvature of the mirror. This image will be the object for the mirror. Image form the mirror will also be formed at the centre of curvature of the mirror and of same size.

So, magnification of the image by this mirror will be $m_{2} = 1$

So, total magnification = $m_{1}$ x $m_{2} = 1$

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