Index of Refraction

1. Index of Refraction Index of refraction of a material equals the speed of light in a vacuum divided by the speed of light in the material.

2. Because of atmospheric refraction, we have lingering, elliptical sunsets. Sun Earth Sun

3. Mirage Cool air Warm air Surface of water?

4. Wave fronts of light qi Air Water qR

5. This bending produces illusions. • Example: Objects in water appear closer and nearer to the surface. Eye Air Water

6. Fish can see everything above the surface of water within a 960 cone.

7. 960

8. Dispersion • Different frequencies are bent different amounts which causes a separation of white light into its constituent colors. • This is the basic principle behind the operation of a prism. We say that a prism disperses the light. • The higher frequencies interact most (slow down the most) and thus are bent the most. • Demo - Aquarium Prism

9. Dispersion in aPrism Slit White Light Source Prism

10. Rainbow

11. Picture - Rainbow • Individual drops act as dispersers. • The 42o cone • Demo– Rainbow Model • A single eye can only see a small range of colors from a single raindrop.

12. Green Flash Earth Sun Dispersion occurs causing multiple images of the sun. The last to set would be blue, but most of the blue has been scattered which leaves green.

13. 6. TOTAL INTERNAL REFLECTION • Video - Laser Under Water • Critical angle is the angle where total internal reflection (TIR) begins. • TIR is possible only when light is entering a medium of lesser index of refraction. • Binoculars make use of TIR.

14. f Principal Axis An eye placed here Imaging with a Convex Lens and passes through a point called the focal point. is bent upon entering the lens. Arrow as Object Upon exiting the lens it is bent again sees an image here. A ray parallel to the principal axis Convex Lens A ray passing through the center of the lens is basically undeflected. This arrangement produces an inverted, real, diminished image.

15. f Principal Axis An eye placed here More Imaging With a Convex Lens is bent upon entering the lens. Upon exiting the lens it is bent again Arrow as Object and passes through a point called the focal point. A ray parallel to the principal axis sees an image here. Convex Lens A ray passing through the center of the lens is basically undeflected. Farsighted people use lenses similar to these. This arrangement produces an upright, virtual, magnified image. It is a simple magnifying glass.

16. f Principal Axis An eye placed here Imaging with a Concave Lens is bent upon entering the lens. Arrow as Object Upon exiting the lens it is bent again A ray parallel to the principal axis such that is appears to have come from a point called the focal point. sees an image here. Concave Lens A ray passing through the center of the lens is basically undeflected. Nearsighted people use lenses similar to these. This arrangement produces an upright, virtual, diminished image.

17. Various Lenses Double Convex Double Concave Plano Convex Plano Concave Convex Meniscus Concave Meniscus Convex lenses are positive converging lenses. Concave lenses are negative diverging lenses.