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An object of height 4.0 em is placed at a distance of 30 cm from the optical centreO' of a convex lens of focal length 20 cm. Draw a ray diagram to find the positionand size of the image formed. Mark optical centre O' and principal focus 'F on thediagram. Also find the approximate ratio of size of the image to the size of the object. |
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Answer» By lens formula,1/f=1/v-1/u1/v=1/f+1/Uv=uf/u+ff=20cm,u=-30cmv=-30*20/-30+20v=-600/-10v=60cmm=v/um=60/-30m=-2v/u=hi/ho60/-30=hi/4hi=-8cm |
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