Wednesday, May 5, 2010

Light Brainpop Summary

There are two types of light; natural light and artificial light. Artificial light is formed when matter gives off energy in the form of light rays. You can produce artificial light in two ways; 1) by heating something up e.g. the wick of a candle or 2) by running electricity through either a solid like a light bulb filaments or through a gas like neon, to produce light. The other type of light is natural light, and there a few different examples. The sun is a natural source of light, and is basically a ball of flame, which is again light in the form of heat. Some animals are also able to produce their own light through chemical reactions in their bodies. Light sources are emitted in a whole spectrum of radiation, called the electromagnetic spectrum, which is a spectrum of "all the possible frequencies of electromagnetic radiation" (Electromagnetic Spectrum, Wikiedia.org). Light can be thought of in two ways, either in waves with electromagnetic field, or sometimes in discreet packets of energy called photons. Because light is an electromagnetic wave, it can travel through space and does not need a medium to travel through. Light travels at roughly 300 k/s, or 299,792,458 m/s. Light travels in straight lines, but when it hits an object it reflects off, and that is why we can see things.

Light Reflecting off a Mirror

Tuesday, May 4, 2010

Flames Optical Illusion

This is the optical illusion we did in class, and although it seems that the flame is coming out of my hand, it is actually an optical illusion, we used a Plexiglas screen, and using the properties of mirrors, we were able to create this illusion. I was behind the screen, while the Bunsen burner was on the other side, and, because a reflected image appears the same distance behind the mirror as it is in front, you can move the Bunsen burner backwards or forwards, then the reflection also moves, and you can make the flame look like its coming out of anywhere. This effect has been used in many movies before computer graphics became as famous.














With a mirror what happens is that when light is reflected, it reflects at the same angle it came, and that is why you can see you self in a mirror. Also, because it reflects in this way, the image always seems to appear at the same distance:


Monday, May 3, 2010

Refraction and Diffraction

Refraction and diffraction 2 different properties of waves, that affect all types of waves. Light normally travels in straight a straight line as long as it is going through the same material. Once is begins going through a different material, it refracts, meaning that it bends, because it travels at a different speed through other materials than it does through air, due to the variation in density, and this causes images to appear bent or distorted. To measure this, we measure the angle of refraction, which is the angle at which a color of light is bent when being refracted. Different colors have different angles of refraction. A prism refracts all colors of light at different angles so that you can see them as a rainbow, as well as rain drops on a sunny day. Diffraction, on the other hand, is "the bending and spreading of waves around different obstacles" (Brainpop: Refraction and Diffraction). Diffraction is like radio waves radiating from a television base, or when you talk. The waves don't all travel in a straight line, but instead in all directions, so that they reach different places. Another example of diffraction is the passing of waves through a small hole. The waves on the other side will spread out. If there is more than one one hole, the waves spread out and overlap, creating a predictable interference pattern. Diffraction can be used, for example, to create x-ray images of small objects, or images of very distant ones.

Diffraction




Refraction