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InterviewSolution
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An object is placed at a distance of 50cm from a concave lens of focal length 20cm. Find the nature and position of the image. |
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Answer» First of all we find out the position of the image which is given by the image distance v. Here, Object distance, u`=-50` cm (It is to the left of lens) Image distance, v=? (To be calculated) Focal length, f`=-20cm` (It is concave lens) Putting these values in the lens formula: `1/v-1/u=1/f` we get, `1/v-(1/-50)=1/(-20)` or `1/v+1/50=-1/20` or `1/v=-1/20-1/50` or `1/v=(-5-2)/(100)` or `1/v=-7/100` or `v=-100/7` So, Image distance, `v=-14.3` cm Thus, the image is formed at a distance of 14.3cm from the concave lens. The minus sign for image distance shows that the image is formed on the left side of the concave lens. We know that a concave lens always forms a virtul and erect image, so the nature of image is virtual and erect. |
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