PH-1758

Converging lenses

Physics · Secondary 4 · Hard · Converging lenses

A converging lens forms a virtual, upright, magnified image of an object placed 20 cm from the lens. The image appears 40 cm from the lens on the same side as the object. Using the lens formula

1/f = 1/u + 1/v

(take

v = -40\,\text{cm}

), what is the focal length

f

$40\,\text{cm}$
$13\,\text{cm}$
$27\,\text{cm}$
$60\,\text{cm}$

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