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.

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

Mirage Warm air Cool air Surface of water?

Air Water ii RR Wave fronts of light

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

Fish can see everything above the surface of water within a 96 0 cone.

96 0

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 PrismDemo - Aquarium Prism

Prism Slit White Light Source Dispersion in a Prism

Rainbow Rainbow

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

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.

6.TOTAL INTERNAL REFLECTION Video - Laser Under WaterVideo - 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.

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

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

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

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