A 2 cm tall object is placed 41 cm from a convex lens with a focal distance of 7 cm. The object is moved to 4cm from the same lens. How would you calculate the distance to the image from the lens, the magnification, and the height of the image?

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Answer 1 · 2016-07-21T07:26:37

$h_i=14/3cm$

$u->"The object distance"=-4cm$

$f->"Focal length of convex lens"=+7cm$

$v->"Image distance"=?$

Lens formula

$color(red)(1/v-1/u=1/f)$

$=>1/v-1/(-4)=1/7$

$=>1/v=1/7-1/4=(4-7)/28=-3/28$

$=>v=-28/3$

$"Magnification"=m=v/u=(-28/3)/-4=7/3$

Again

$"Magnification"="Height of image"/"Height of object"=h_i/h_o$

Given height of object $h_o=2cm$

$:.h_i/h_o=7/3=>h_i=h_o xx7/3=2xx7/3$

$h_i=14/3cm$