Final answer:
An achromatic lens is made of two converging lenses with focal lengths of f1 = 28.1 cm and f2 = 25.1 cm. The combination is converging and has a net focal length of approximately 14.41 cm.
Step-by-step explanation:
An achromatic lens is a combination of two lenses, each with a different focal length. The first lens has a focal length of f1 = 28.1 cm, and the second lens has a focal length of f2 = 25.1 cm.
To determine if the combination is converging or diverging, we need to compare the focal lengths. Since both lenses have positive focal lengths, they are both converging lenses. When two converging lenses are placed in contact, the net focal length is given by the equation: 1/f = 1/f1 + 1/f2. Substituting the given values, we get:
1/f = 1/28.1 + 1/25.1
Solving for f, we find that the net focal length of the achromatic lens is approximately 14.41 cm.