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A beam of light converges at a point P. Nnw a lens is placed in the path of the convergent beam 12cm from P. At what point does the beam converge if the lens is (a) a convex lens of focal length 20 cm, and (b) a concave lens of focal length 16 cm ? |
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Answer» SOLUTION :`(1)/(v) - (1)/(u)= (1)/(f)"" f = 20 ` cm , u = + 12 cm( OBJECT on the right) `(1)/(v) = (1)/(20) + (1)/((+12)) = (20 + 12)/(20 xx 12) = (32)/(240) = (2)/(15)"" therefore v = 7.5 ` cm A real image is formed 7.5 cm away from the lens. b. `(1)/(v) = (1)/(f) + (1)/(u)= (1)/(-16) + (1)/(12) =(-12 + 16)/(16 xx 12) = (4)/(16 xx 12)= (1)/(48)therefore v= 48` cm A real image is formed at 48 cm away from the lens |
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