Prisms, total internal reflection, polarization, how we see color, how vision is corrected and rainbows. Light and Color

Refraction The bending of light as it passes from one medium to another. Dependent upon –Change in light wave speed –Change in direction Bending means an abrupt change in direction.

Prisms High frequency light in a transparent medium travels slower than low frequency light (red light travels faster than violet light) Thus, the different colors are refracted at different angles. When white light is refracted twice, and the second surface is not parallel to the first, the dispersion is noticeable, thus the colors are observed. If the two boundaries of the medium are parallel, the refractive effects at the first boundary are reversed at the second boundary.

Total Internal Reflection Light can be reflected off a transparent medium boundary at a certain angle. This angle is called the critical angle. Fiber Optics

Total Internal Reflection

Polarization of Light Light consists of waves vibrating in all planes (360 o ). A polarizer allows only the light wave along one plane to pass through. Two polarizers if oriented at right angles will cancel all light. Glare (reflected light polarized in a plane parallel to a non-metallic surface) is greatly reduced when using polarized lenses. olarizers/Polarizer.htm olarizers/Polarizer.htm

Colors:additive and subtractive add.html add.html

The Eye and its Structure Focusing lenses (double convex lens system) –Cornea (convex lens)--main focusing, fixed –Lens (convex lens)—fine focusing, adjusts Pupil (light regulator) Retina (back of eye) –Rod cells (senses intensity) –Cone cells (red, green and blue light receptors)

Rods and Cones in the Retina Retina (back of eye) –Rod cells (senses intensity) –Cone cells (red, green and blue light receptors

Rods and Cones C/CC/vision_background.html C/CC/vision_background.html ml ml <> <> <> <>

Colorblindness Colorblindness is a deficiency in the number of red, green or blue cones (too few of one or more cone types). Normal vision Colorblindness

Better Eyes humanvision/accommodation/index.html humanvision/accommodation/index.html

What is color? When we see color, we are seeing specific frequencies of visible light VISIBLE LIGHT IS ROYGBIV Red, orange, yellow, green, blue, indigo and violet For visible light –Red has the lowest frequency and longest wavelength –Violet has the highest frequency and shortest wavelength

When sunlight passes through a prism, it separates into a spectrum of all the colors of the rainbow The Color Spectrum roygbiv

Isaac Newton—discovered that white light is composed of seven different colors of light White Light Red Orange Yellow Green Blue Indigo Violet A prism disperses white light into its primary frequencies of color

Prisms /prism.html /prism.html

a. This square reflects all the colors illuminating it. In sunlight, it is white. When illuminated with blue light, it is blue. b. This square absorbs all the colors illuminating it. In sunlight it is warmer than the white square Color by Reflection

Why a shirt appears blue. A blue shirt appears blue in white light because it reflects only blue and absorbs red and green (or the other colors) A blue shirt appears black in red light because it absorbs red and reflects nothing. A blue shirt appears blue in blue light because is reflects blue. A white shirt appears blue in blue light because it can reflect blue light.

The Eye and Colors