How light travels through prisms
Ellen Hederick
November 7 2018
Waves Blog
How light travels through prisms
When light enters a prism the light bends. “White light entering a prism is actually made up of lots of different types of light”. Lights of different colors have different "wavelengths" (this is the distance between the peaks of two waves. When we see colors our eyes are sensing the different wavelengths and we see these different wavelengths as color. When white light enters a prism, each type of light within that white light (which is all the colors) are then all reflected at different angles because of all the different wavelengths. By doing this the light waves effectively separate all of the colors present in the white light into different bands (which we can see as the spectrum or the prism monochromator). The separation of visible light onto different colors is called dispersion. Refraction is a phenomenon that happens when a white beam of light passes through the interference between air and a denser medium. A couple of examples of that is glass or water. The denser the medium the slower the light moves through it, so it changes direction or refracts.
We see about 6 colors (red, orange, yellow, green, blue, and violet) when we look at a rainbow. Occasionally we see indigo. All of these colors that I have listed have an association with different wavelengths of light. “When our eye receives pure-wavelength light, we tend to see only 6 colors depending of the wave length”. Did you know that sunlight is considered white? It actually appears to be a little bit yellow because of its mixture in wavelengths. White light is a mixture of all the different wavelengths of light. Each individual wavelength refracts at a slightly different angle. “ Therefore, when the beam emerges from the denser medium, it has been split into its component wavelengths. The ones you can see form the familiar rainbow”. Generally we all think a rainbow is several different colors but actually it is a continuum with no discrete boundaries from one hue to another. “It was Isaac Newton who arbitrarily spilt the spectrum into seven colors in deference to the ancient Greeks, who believed seven to be a mystical number”.
The index of refraction is also very important to this topic. This is a property derived by dividing the speed of light inside a vacuum by the speed of light in that specific medium. The angle of refraction in a particular medium is defined by its index of refraction”. When light passes from one medium to another, the angle of the refraction can be derived (or obtained from a certain source) by dividing the idicuts of refraction of the two media. The relationship between these is also known as Snell’s Law, named for the 17th century physicist who discovered it. Not only glass produces rainbows, several other types of materials can produce rainbows also. Several examples are diamond, ice, clear quartz, and glycerine, however, those are only a few examples out of many. The breadth of a rainbow is a function of the index of the refraction, which can vary directly with the density of the material. Did you know that you can even see a rainbow when light passes from water through a clear crystal or a piece of glass and back into water?
http://scienceline.ucsb.edu/getkey.php?key=4498
https://kids.britannica.com/kids/assembly/view/87682
https://www.physicsclassroom.com/class/refrn/Lesson-4/Dispersion-of-Light-by-Prisms
https://sciencing.com/happens-light-passes-through-prism-8557530.html
Comments
Post a Comment