Radiolab hosted an interesting podcast on colors and has a few interesting points that they made. They spoke about how we perceive colors differently and if we were to be visited by aliens, would they see the same colors we were seeing. They also went on to speak about dogs and how dogs have color vision in the colors of blue/yellow and black/white. This was all led into by a discussion of the prism developed by Sir Isaac Newton. Upon looking into prisms I discovered that “Light changes speed as it moves from one medium to another (for example, from air into the glass of the prism). This speed change causes the light to be refracted and to enter the new medium at a different angle (Huygens principle). The degree of bending of the light's path depends on the angle that the incident beam of light makes with the surface, and on the ratio between the refractive indices of the two media (Snell's law). The refractive index of many materials (such as glass) varies with the wavelength or color of the light used, a phenomenon known as dispersion. This causes light of different colors to be refracted differently and to leave the prism at different angles, creating an effect similar to a rainbow. This can be used to separate a beam of white light into its constituent spectrum of colors. Prisms will generally disperse light over a much larger frequency bandwidth than diffraction gratings, making them useful for broad-spectrum spectroscopy. Furthermore, prisms do not suffer from complications arising from overlapping spectral orders, which all gratings have. Prisms are sometimes used for the internal reflection at the surfaces rather than for dispersion. If light inside the prism hits one of the surfaces at a sufficiently steep angle, total internal reflection occurs and all of the light is reflected. This makes a prism a useful substitute for a mirror in some situations.” Getting back to the original topic, they discussed how colors are seen outside the mind and completed inside the mind which is why Sir Isaac Newton was able to see a purple daisy even though the actual color of the daisy he was looking at was in fact yellow. Newton’s work with colors and prisms was to prove his point that light alone was the only thing responsible for colors. Upon further investigation I found that “Newton set up a prism near his window, and projected a beautiful spectrum 22 feet onto the far wall. Further, to prove that the prism was not coloring the light, he refracted the light back together. Artists were fascinated by Newton’s clear demonstration that light alone was responsible for color. His most useful idea for artists was his conceptual arrangement of colors around the circumference of a circle (right), which allowed the painters’ primaries (red, yellow, blue) to be arranged opposite their complementary colors (e.g. red opposite green), as a way of denoting that each complementary would enhance the other’s effect through optical contrast.”