How does an achromatic lens help reduce chromatic aberration?

An achromatic lens is designed specifically to minimize chromatic aberration, a common optical distortion where different colors of light are focused at different points because they refract at varying angles through a lens. This phenomenon occurs due to the dispersion of light, which is the different bending of wavelengths as they pass through a medium, such as glass.

The correct answer highlights the construction of achromatic lenses, which typically involves combining two different types of glass with varying refractive indices. One type of glass is chosen for its ability to focus short wavelengths of light (like blue), while the other compensates for longer wavelengths (like red). By carefully selecting these two materials and arranging them in a specific way, the lens can be designed to bring these colors to a common focal point, thus significantly reducing chromatic aberration.

This principle of combining glasses exploits their complementary optical properties, which enhances the lens's overall performance in producing clearer and sharper images across a range of wavelengths. The result is a lens that effectively corrects color fringing and improves image quality.