Hydrolysis of d-sucrose results in change of optical rotation because :

number of moles of d-glucose are less than the number of moles of l-fructose produced during hydrolysis,

both glucose and fructose are levorotatory.

glucose is l and fructose is d and number of moles of glucose formed during reaction a,· greater than number of moles of fructose.

angle of rotation of l-fructose is greater than that of d-glucose.