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A convex lens of focal length 20 cm produces images of the same magnification 2 when an object is kept at two distances x1 and x2 (x1>x2) from the lens.  The ratio of x1 and x2  is :

(a)

3:1

(b)

2:1

(c)

4:3

(d)

5:3


Question ID - 51288 | Toppr Answer

A convex lens of focal length 20 cm produces images of the same magnification 2 when an object is kept at two distances x1 and x2 (x1>x2) from the lens.  The ratio of x1 and x2  is :

(a)

3:1

(b)

2:1

(c)

4:3

(d)

5:3

1 Answer - 5876 Votes

3537

Answer Key : (a) -

∴   −  =

∴   v = (±2u)

∴   + =  ⇒  =

∴    u1=30 cm

And    =

∴    =

∴   u2=10

∴      = 3.



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