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A converging lens with a focal length of 10 cm ... - SS2 Physics Geometrical Optics Question

A converging lens with a focal length of 10 cm is used to form an image of an object placed 20 cm in front of the lens. The image distance is:

A

5 cm

 

B

10.5 cm

 

C

6.67 cm

 

D

40.56 cm

correct option: c

Focal length (f) = 10 cm

Object distance (u) = -20 cm (negative sign indicates the object is placed in front of the lens)

1/10 = 1/v - 1/-20

1/10 = (20 - v) / (20v)

20v = 10(20 - v)

20v = 200 - 10v

30v = 200

v = 200 / 30

v ≈ 6.67 cm

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