InterviewSolution
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InterviewSolution
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A convex lens of focal length 10 cm is placed at a distance of 12 cm from a wall. How far from the lens should an object be placed so as to form its real image on the wall? |
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Answer» Here, the real image is formed on the wall which is at a distance of 12 cm from the convex lens. This means that the distance of image from the convex lens or image distance will be 12 cm. Since a real image is fomred on the right side of the lens, so this image distance will be positive. Now, Image distance, `v=+- 12` cm (A real image) Object distance, u=? (To be calculated) Focal length, f=+10 cm (it is convex lens) Putting these values in the lens formula: `1/v-1/u=1/f` We get: `1/12-1/u=1/10` `1/12-1/10=1/u` `(5-6)/(60)=1/u` `-1/60=1/u` So, Object distance, u=-60 cm Thus, the obect should be place at a distance of 60 cm in front of the convex lens. The minus sign shows that the obect is on the left side of the lens. |
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