If the there are more CSF fuild inside the skull than usual what will happen to the light inside?

If there is more cerebrospinal fluid (CSF) inside the skull than usual, the light inside will expand, producing a condition known as hydrocephalus.

Explanation:

The cerebrospinal fluid is a colorless, crystalline substance that provides protection to the central nervous system by cushioning any trauma received and supporting its structures, as well as providing nutrients.

This fluid is produced within the cerebral ventricles, mostly by the activity of the choroidal plexuses, and is found within the ventricles, in the ependymal canal, circulating through the subarachnoid space.

An increase in the amount of cerebrospinal fluid -due to increased production or obstruction of its reabsorption- will cause an expansion of the cavities that contain it, such as the cerebral ventricles, producing a condition called hydrocephalus.