InterviewSolution
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InterviewSolution
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A convex lens of focal length 20cm is placed 10cm away from a second convex lens of focal length 25 cm. What wil be the location of the image of an object at 30 cm in front of the first lens? |
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Answer» Let the image from the first lens be formed at a distance y to the right of lens. Refraction at the first lens: Here, `u=-3cm, f=+20cm, v=+y` From the lens equation, we get `(1)/(v)-(1)/(u) =(1)/(f_(1))` or `(1)/(y)-(1)/(-30) =(1)/(20)or y=60cm` Refraction at the second lens: Here, `u=60-10=+50cm, f=+25cm` Let the image be at a distance z to the right of lens2. Therefore, `v=+z. ` Substituting in the lens equation, we get `(1)/(v)-(1)/(u) =(1)/(f_(2))` or`(1)/(z)=(1)/(25) +(1)/(50) or z=(50)/(3) cm` |
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