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I'm sure we all remember the poplular Youtube hit where the hiker becomes completely overwhelmed with emotion at the sight of a "double rainbow all the way across the sky." So, maybe his reaction was slightly over dramatic, but the science behind the phenomenon is pretty exciting. Try to contain yourselves though. In order for a rainbow to form, there are a couplel conditions: there must be a lot of moisture in the air and the sun must be behind us. Sunlight is white and is made up of the combination of frequencies from the colors in the visible light spectrum . When the sunlight hits the droplets of water, they act as miniature prisms. The white light is refracted into the drop at the boundary between air and water. The difference in mediums and and the increase in the index of refraction causes the light to slow down and change direction. Then it is reflected off of the inside of the back of the drop and refracted once again as it exits the drop, this time being dispersed into the white light's components on the visible light spectrum: red, orange, yellow, green, blue and violet. The angle of reflection inside the drop is between 40 and 42 degrees. Although each individual drop disperses the entire visible light spectrum, the rainbow appears to be split into separate bands of color. This is because our eye percieves the drops that lie at a steeper angle to be red and the drops that lie at a less steep angle to be violet. Therefore, a rainbow appears differntly to different observers depending on their location. When the sun reaches an angle above 42 degrees in the sky, the rainbow will dissapear. A rainbow is not a fixed point or a tangible object, it is only the way our eye percieves refracted light at 40- 42 degrees. So what about the legendary double rainbow? A double rainbow is formed when the sunlight is reflected at two points on the inside of the raindrop instead of just one. This second reflection creates a secondary rainbow at an angle of 50-53 degrees, making it appear higher in the sky. The colors are in reverse order because the light is bent again as it leaves the raindrop. Circular rainbow?? Yes, rainbows are actually circular. From the ground we only see the top half of the circle because of the presence of the ground. If you were to see a rainbow from an airplane you may see the entire circle.

Name: Sprinkler Rainbow Conspiracy Category: Optics Date Added: 2015-08-11 Submitter: FizziksGuy The "conspiracy" about rainbows from sprinklers. Sprinkler Rainbow Conspiracy

Last night I happened to look up as I was walking inside at around 10 and noticed that I could see a lot of stars. Like a lot. I am quite a fan of stargazing but despite owning a telescope I have always done it with my naked eyes. But I was in the mood to see some planets in detail so I lugged down the old telescope from the attic and dusted her off only to make a distressing discovery- all the eyepieces were missing (you need those if you want to see anything). My dad and I scoured the dust and cobweb infested boxes in our attic for half an hour but came up empty handed, and I had to resign to reading a book. Now that you have gotten through my exceptionally boring story, I would like to tell you how telescopes work. The basic function of a telescope is to collect, focus and magnify the light emitted from celestial bodies (stars, planets, nebulae, galaxies, ect...). In many cases, it is actually more important to collect and filter light than it is to magnify it. The ability of a telescope to collect light is related to it's aperture- which is it's lens or mirror diameter- and it's ability to magnify depends on magnification. Aperture is usually harder to expand as it depends on the diameter of the telescope tube but magnification can be changed as easily as screwing in a new eyepiece. The first telescope created by Galileo was a refracting telescope. Contrary to popular belief, Galileo did not invent this technology but he was the first to apply it to the art of stargazing. Refracting scopes use a large objective lens at the front of the tube to collect and bring light into a focal point in the middle of the tube. From there it can be focused and magnified by the eyepiece. Below is a diagram of how light travels through refracting lenses. Check out my next post for reflecting telescopes and closing thoughts.