The Huygen's telescope eye piece

ANS:C - both (a) and (b)

Huygens' eyepiece satisfies the condition for achromatism because the two lenses are made from different types of glass, each with a different refractive index and dispersive power. The eyepiece lens is made from a crown glass with a lower refractive index, while the field lens is made from a flint glass with a higher refractive index.