Find the focal length of a convex lens which produces a virtual image at 10 cm from the lens when an object is placed at 5 cm from the lens.

Explanation

To find the focal length of a convex lens that produces a virtual image, we can use the lens formula:

\[ \frac{1}{f} = \frac{1}{v} - \frac{1}{u} \]

where:
- \( f \) is the focal length of the lens,
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