It looks great, except, I would rewrite the first sentence as "Everett knew it was dangerous to be within close proximity to a cheetah". Also, in the second sentence, I would get rid of the words "at the moment". They aren't really necessary. That's all. Everything else looks perfect. Good job introducing the subject, by the way.
The different reflections of light through two separate mediums causes the bending of wave fronts associated with light rays. The reflection and refraction is caused by the medium associated with its light rays.
