Question

Which one is a laevorotatory sugar?
(A) Sucrose
(B) Glucose
(C) Fructose
(D) None of the above.

Answer 1

Hint: A chemical compound or any other substance that rotates the plane polarized light to the anti-clockwise direction is called a laevorotatory substance. If the direction of rotation of the plane polarized light is in the clockwise direction then it is called the dextrorotatory sugar.

Complete Step by Step Answer
When the plane-polarized light is passed through a solution then the direction of the light can be rotated to either clockwise or to anticlockwise directions. The phenomenon of the rotation of plane polarized light is called “Mutarotation”. If the direction of rotation is in the anticlockwise direction or the left side then it is called laevorotatory and if the direction of rotation is in the clockwise direction or the right side then it is called dextrorotatory. An example of the laevorotatory sugar is Fructose, as it is also named as levulose. Fructose is a monosaccharide and is commonly found in fruits such as dates. It is the most sweet of all the sugars. It combines with glucose to form sucrose. Ordinary glucose is dextrorotatory. Sucrose is also dextrorotatory.
Hence, the correct option is C.

Note
Light is an electromagnetic radiation in which the electric and the magnetic fields are perpendicular to each other in the direction of their propagation. In a plane polarized light, the component electric field oscillates just like that in an ordinary light and the direction of propagation takes place in a single plane. Likewise the component magnetic field also oscillates in a single plane and both the planes being perpendicular to each other.