A convex mirror of focal length 10cm is kept at a distance of 30cm front of a 4cm high object.Find the height of the image of the object?

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Answer 1 · 2018-05-11T12:58:22

$"the length of the image is 1 cm."$

$-1/f=1/u-1/(u')$

$"where f is the focal length, u is the distance between the object and the mirror, "$ u' $" is the distance from the image to the mirror."$

$"Since the focus and the image are behind the mirror, their signs is negative."$

$f=10" " cm$
$u=30" "cm$
$"let us calculate the image length using formula."$

$-1/10=1/30-1/(u^')$

$1/(u^')=1/10+1/30$

$1/(u^')=(3+1)/30$

$1/(u^')=4/30$

$u^'=7.5" " cm$

$g/c=(u')/u$

$"where g is the length of the image, c is the length of the object."$

$g/4=(u^')/u$

$g/4=(7.5)/30$

$g/4=1/4$

$g=1 cm$