The Effect of Interference and Diffraction In the end, though, the two names describe the same concept. When there are many different sources, it’s usually called wave diffraction. However, when most scientists talk about a small amount of sources diverting light waves, it’s usually called wave interference. They are designations that don’t have a firm difference between the two. So, is there a difference between interference and diffraction? The scientific answer is this: not really. This effect is called interference or diffraction. When waves are diverted by particles in the air or other light waves, their path and even their wavelength can change. However, it’s when light waves take a detour on the way to our eye that they react in unique and colorful ways. When light waves travel to our eyes on a straight and unimpeded path, we discern colors in a fairly straightforward fashion. So where does interference and diffraction come into this picture? These waves travel from a source and help us discern both light and color. Right in the middle of the electromagnetic spectrum are light waves. X-rays are harnessed by special machines that allow us to view inside our bodies. Microwaves cook our food through the power of (unsurprisingly) microwaves. Radio stations transmit their signal via sound waves. Some of these waves we are able to discern, but others are beyond our abilities to process. Waves can carry different types of information, like light and sound. Waves are part of the electromagnetic spectrum, and they carry information from one place to another. So what exactly is this phenomenon?īefore we consider interference and diffraction, we have to take a moment to consider what light is and how it travels. Not only do you see them in rainbows and CD’s but you can also observe them in bubbles, glass, and holographic stickers (just to name a few). Have you ever wondered how these kaleidoscopes of colors are produced? They are all around us. Why does the CD react like this? It’s simple: the principles of interference and diffraction are at work, causing you to see these gleams of color. How about a more man-made phenomenon? As you spin a CD back and forth between your fingers, the back of the disc flashes a brilliant array of colors. Of course, there’s no pot of gold at its end, but there is a wealth of knowledge that the rainbow can teach us about wave diffraction. So if you hold a hair straight up through the middle of your laser beam right next to the pointer, you'll get the same diffraction pattern out as you would have if you'd shot the beam through a single slit of the same size.As you look at the horizon after a rainstorm, you see it in looming in the distance. Because of Babinet's Principle, a slit in the middle of a barrier gives pretty much the same diffraction pattern as just a barrier of the same size as the slit. You can actually prove this yourself with a hair and a laser pointer. The only reason I could think of for HAVING a lens would be to have a converging lens focus an interference pattern town to a smaller area (say, if you want to save a meter wide interference pattern on a 5 mm CCD chip). In the correct place in between them, you get destructive interference. These particular wavelets represent the PEAK of a wave, so wherever the wavelets intersect, you get constructive interference. We can think about that in terms of Huygens' Principle, where instead of rays, you represent light as a bunch of little wavelets like below. Rays will automatically "converge" on their own due to diffraction. You don't need to place a lens between your slit plane and your screen for either a Young's double slit setup or for a typical single slit setup.
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