|  | 3.2 |
| Optical Media
|  | 3.2.4 |
| Refraction
When a light strikes the interface between two transparent materials, the light divides into two parts. Part of the light ray is reflected back into the first substance, with the angle of reflection equaling the angle of incidence. The remaining energy in the light ray crosses the interface and enters into the second substance. If the incident ray strikes the glass surface at an exact 90-degree angle, the ray goes straight into the glass. The ray is not bent. However, if the incident ray is not at an exact 90-degree angle to the surface, then the transmitted ray that enters the glass is bent. The bending of the entering ray is called refraction. How much the ray is refracted depends on the index of refraction of the two transparent materials. If the light ray travels from a substance whose index of refraction is smaller, into a substance where the index of refraction is larger, the refracted ray is bent towards the normal. If the light ray travels from a substance where the index of refraction is larger into a substance where the index of refraction is smaller, the refracted ray is bent away from the normal. Consider a light ray moving at an angle other than 90 degrees through the boundary between glass and a diamond. The glass has an index of refraction of about 1.523. The diamond has an index of refraction of about 2.419. Therefore, the ray that continues into the diamond will be bent towards the normal. When that light ray crosses the boundary between the diamond and the air at some angle other than 90 degrees, it will be bent away from the normal. The reason for this is that air has a lower index of refraction, about 1.000 than the index of refraction of the diamond.
|  | Interactive Media Activity
Interactivity: Optical Refraction This activity shows how refraction works in different materials (starting from a vacuum). Interactive Media Activity 3.2.4 is located in the CCNA 3.0 Bridge 1 Activities and Quizzes file. The Activities and Quizzes file can be downloaded in the Course Material section of your class homepage.
Web Links
The Transmission of Wave through Dense media – Reflection and Refraction http://www.phy.ntnu.edu.tw/java/ propagation/ propagation.html