An object 60cm from a lens gives a virtual image at a distance of 20cm in front of the lens. What is the focal length of the lens? Is the lens converging or diverging? Give reasons for your answer.
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u = -60cm v = -20cm (Virtual image)$\frac{1}{\text{f}}=\frac{1}{\text{v}}-\frac{1}{\text{u}}$
$\frac{1}{\text{f}}=\frac{1}{-20}-\frac{1}{-60}$
$\frac{1}{\text{f}}=\frac{-2}{60}$
$\text{f}=-30\text{cm}$
The lens is diverging because the focal length is negative.
$\frac{1}{\text{f}}=\frac{1}{-20}-\frac{1}{-60}$
$\frac{1}{\text{f}}=\frac{-2}{60}$
$\text{f}=-30\text{cm}$
The lens is diverging because the focal length is negative.
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