In the lens equation, the variable do represents the distance of the object from the blank

Optical centre

Explanation:

In case of lenses or mirrors, all the distances are measured from the centre of lens or centre of mirror.

The centre of lens is called optical centre.

Do is the distance of object from the optical centre and Di be the distance of image from the centre of lens.

molecules are free to separate from each other and will take on the shape of the container. molecules move completely at random and high speeds. they vibrate in a fixed position and do not move around much. molecules expand to the edge of their container.