When the image is formed at the near point ( 25 cm ) of a normal eye, a simple microscope exhibits a magnifying power of 3.0 . Determine the focal length of the microscope.

Step-by-step solution

The magnifying power of a simple microscope when the image is formed at the near point is given by the formula: m = 1 + D f where m is the magnifying power, D is the least distance of distinct vision (near point), and f is the focal length of the lens. Given: m = 3.0 D = 25 cm Substituting the given values into the formula: 3.0 = 1 + 25 f 2.0 = 25 f f = 25 2.0 = 12.5 cm The focal length of the microscope is 12.5 cm .