Vocab

1. Vocab Refraction Refracted Ray The change in direction of light as it passes from one material to another Bend Water -> air Light refracts when it travels from air to water or from water to air

2. Vocab Optical Density How difficult it is for light to pass through a substance Determines the change in direction of light as it passes from one substance to another The greater the difference in optical densities the greater the degree of bending between.

3. Vocab Index of refraction n Unique for every substance Always greater than 1 A measure of the speed of light in a specific substance. The index of refraction of water is 1.33, meaning that light travels 1.33 times faster in vacuum than it does in water.

4. + Vocab Converging Lens A lens that is thicker in the center than at the edge • Cross • Come together • Intersect • glasses Parallel light rays that travel through a Converging Lens will cross / intersect / come together on the other side. The focal length of a converging lens is Positive

5. Principle focal point Vocab - + Diverging Lens A lens that is thinner in the center than at the edge • Separate • Different directions • Disperse • Hourglass (?) The focal length of a diverging lens is Negative on the side where light diverges. It is positive on the side where light would converge.

6. Vocab Critical Angle • Incident angle The incident angle at which light refracts along the boundary between 2 substances If the incident angle is less than the critical angle light will refract. If the incident angle is more, it will reflect

7. Vocab Total Internal Reflection • Material acts like a Mirror • Incident angle = reflected angle When light reflects off of the boundary between 2 substances instead of refracting Total internal reflection can only occur when light is traveling from a high optical density to a low optical density and: incident angle > critical angle