Light also will not be refracted if it hits at an angle beyond a certain point. Instead, it will reflect the ray of light. The angle in question is known as the critical angle. If the angle of incidence is less then the critical angle, then the ray of light would refract close to the border of both materials. When the angle of incidence is the exact same as the critical angle, the light is both reflected and refracted, and as stated earlier, if the angle of incidence is greater than the critical angle, then the ray of light would reflect instead of refracting. So if a ray of light were to continuously hit the inside walls at an angle greater than the critical angle, the ray of light would be reflected each time. This phenomenon is known as Total Internal Reflection, and is used in technologies such as fiber optic wires.
![Picture](/uploads/4/7/8/0/47808873/3268626_orig.gif)
As you can see, the green ray hits the inner wall of the denser material at an angle less than the critical angle, thus being refracted. The red ray hits at an angle equal to the critical angle, so the ray refracts and reflects. Finally, the blue ray hits at an angle greater than the critical angle, thus reflecting off of the inner wall.