An achromatic combination of lenses produces
a)	Images in black and white
b)	Coloured images
c)	Images unaffected by variation of refractive index with wavelength
d)	Highly enlarged images are formed

(c)

The image of an object in white light formed by a lens is usually coloured and blurred. This defect of image is called chromatic aberration and arises due to the fact that focal length of a lens is different for different colours. In case of two thin lenses in contact, the combination will be free from chromatic aberration. The lens combination which satisfies this condition is called achromatic lenses.