Given: u = -6 cm (the object is 6 cm from the eye, and the direction is negative), v = 10 cm (the image is 10 cm from the eye) Using the lens formula: \(\frac{1}{\text{f}}\) = \(\frac{1}{\text{v}}\) - \(\frac{1}{\text{u}}\) \(\frac{1}{\text{f}}\) = \(\frac{1}{10}\) + \(\frac{1}{6}\) \(\frac{1}{\text{f}}\) = \(\frac{8}{\text{30}}\) So that f = 3.75cm upon cross multiplying Therefore, the focal length of the lens is 3.75 cm.