ATMS 120 1st Edition Lecture 11 Outline of Last Lecture I Weather around fronts II Freezing rain how it forms III Freezing rain where it occurs Outline of Current Lecture I Light and color perception by the human eye II Color III Blue skies IV Sunsets V Rainbows Current Lecture I The range that humans can see visible spectrum is between 0 38 0 78 micrometers Some animals have a visible spectrum outside of humans The rods in our eye respond to all wavelengths of visible light They allow us to see light and dark black and white If we all only had rods everyone would be color blind The cones in our eyes respond to different wavelengths of light Some cones are stimulated by red while others blue and green etc Our eyes are able to create colors magenta and brown for example are not in the visible color spectrum but our eyes combine colors to create these new ones in a sense II White vs black White all colors are perceived by the eye at the same intensity Black the absence of color either because it is blocked or because it is absorbed Technically we have never seen the color black Color visible light of a different frequency that strikes the eye Colors are either reflected or emitted They are not the same concept Fire for example emits light because it is let off as energy in heat Traffic lights work the same way the light is very very hot A yellow shirt however is a reflection The shirt itself is not producing any energy therefore it is not emitting the color we see These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute The wavelength of maximum emission on the sun is actually blue not yellow Oceans appear blue because the sky is blue not the other way around III Long wavelength Short wavelength Red Orange Yellow Green Blue Indigo Violet When colors hit the top of the atmosphere the longer wavelength colors go right through to the earth s surface for the most part The shorter wavelengths of light however blue indigo violet scatter once they hit the top of the atmosphere reflecting light in all directions Visible light is scattered by air molecules The efficiency of the scattering is dependent on wavelength Blue light is 10 times more efficiently scattered than red light IV When the sun sets the path length of the sun s rays through the atmosphere is at its longest When the sun is directly overhead the path is shorter On the horizon the amount of light that gets scattered increases and more wavelengths get scattered The shorter wavelength light is completely scattered away while the longer wavelength yellow orange and red survive the trip Really red sunsets indicate that the air is really dirty the other wavelengths are blocked V Refraction the bending of light as it passes from one medium to another An example of this is air to water The densities of the two mediums differ so the image that we see is a refraction of the object What happens inside the raindrop to produce a rainbow Light is refracted then reflected then refracted again The density of the droplet is less than the density of the air Different colors wavelengths of light are reflected at different angles totaling 2 degrees in total This is why rainbows are arced at 2 degrees as well For a rainbow to work there must be rain and sunshine and you must be facing the rain with the sun to your back Rainbows technically make a complete circle but from the ground we only observe the arc When you observe a double rainbow the colors of the second rainbow the outside one are opposite a primary rainbow