What is the purpose of the reflective material in the choroid coat? what is it called?

Purpose: to impart better night vision to nocturnal animals by increasing the available light for photoreceptors.

It is called "tapetum lucidum".

Explanation:

The reflective material in the choroid coat of some nocturnal vertebrates is called "tapetum lucidum". Its function is to improve the night vision of nocturnal animals. The tapetum lucidum serves to reflect the dim light available in the night. The reflected light re-stimulates the photoreceptor cells present in the retina. This increases the available light for night vision.

Tapetum lucidum makes the eyes of nocturnal mammals to shine at night.

explanation:

the universal gravitation equation. since the gravitational force is directly proportional to the mass of both interacting objects, more massive objects will attract each other with a greater gravitational force. if the mass of one of the objects is doubled, then the force of gravity between them is doubled.