Achromatic combination of lenses is the combination of two lenses of different nature and of different focal lengths. ... If we combine a convex and concave lens properly, the focal length of the combined lens will not change for different wavelengths of light. This combination of lenses is known as achromatic lens.

What is an achromatic combination of prism?

: a prism made by combining two or more prisms of different refractive index so designed and placed that a ray of white or other nonhomogeneous light passing through the prism is deviated but not dispersed into a spectrum — compare amici prism.

Which combination is used in formation of achromatic lenses?

Let's define achromatic lens as the combination of two different types of lens of different focal lengths such that the image formed by the combination of these two lenses is free from chromatic aberrations. To do so, we combine one convex lens and one concave lens and place them next to each other.