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As shown in the figure, a thin rod AB of...

As shown in the figure, a thin rod AB of length 10 cm is placed on the principal axis of a concave mirror such that it.s end B is at a distance of 40 cm from the mirror. If the focal length of the mirror is 20 cm, find the length of the image of the rod

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`rArr` / = 20 cm and the end B is at distance 40 cm = 2f = R. Thus the image of B is formed at B only. Now for end A, u = - 50cm, f = - 20 cm, v=?
In `1/u + 1/v = 1/f,` putting these values
`- 1/50 + 1/v = - 1/20`
`therefore 1/v = 1/50 -1/20 = (20-50)/(20 xx 50) = - (30)/(1000)`
`therefore v = - (1000)/(30 = - 33.3 cm `
This image `Lambda` is on the same side as the object Now, length of the image = 40 - 33.3 = 6.70 cm
=0 .0670 m
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