An invert sugar is laevorotatory. Sucrose is known as 'invert sugar'. After hydrolysis it gives dextrarotatory glucose and laevorotatory fructose. Since the laevorotation of fructose $\left(-92.4^{\circ}\right)$ is more than dextrarotation of glucose $\left(+52.5^{\circ}\right)$, the mixture obtained is laevorotatory.