# Use the lens formula to find where a convex lens with a 5cm focal length will form an image for an object that 15cm away?

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- Old Science GuyLv 711 months agoFavourite answer
1/f = 1/di + 1/do

convex glass lens in air is a converging lens so f is positive

1/5 = 1/di + 1/15

1/di = 1/5 - 1/15 = 2/15 = 1/ 7.5

di = 7.5 cm

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- MyRankLv 611 months ago
Given,

Focal length (f) = 5cm = 5 x 10⁻²m

Object distance (u) = 15cm

Image distance (v) = ?

Using len’s maker’s formula:-

1/f = 1/v + 1/u

= ½ = 1/v + 1/15

= 1/v = 1/5 – 1/15 = 3-1/15 = 2/15

= v = 7.5

∴ Image distance (d) = 7.5cm.

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