This is the speed of light in vacuum divided by the speed of light in the medium. this determines the amount of bending of a light wave

Refractive index.

Explanation:

Refractive index or the index of refraction may be defined as the quantity that measures how fast the light travels in different media. Different materials have different refractive index.

Refractive index can be calculated by the formula by dividing the speed of light in vacuum with the speed of light in different media. The amount of refraction and the bending of light as light enters from one media to another is shown by the refractive index.

Thus, the answer is refractive index.

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.