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| howto:hambasics:waveinterference [2019/10/05 14:30] – ve7hzf | howto:hambasics:waveinterference [2019/10/05 15:46] – [Wave Addition] ve7hzf |
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| <box orange 100% |**Under Construction**> | <box orange |**Under Construction**> |
| VE7HZF is editing this section, please do not edit it until this notice is taken down. | VE7HZF is editing this section, please do not edit it until this notice is taken down. |
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| ====== Interference ====== | ====== Interference ====== |
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| An important property of waves (radio, sound, water, or otherwise) is that they can interfere with one another. Here's a Veritasium video showing two waves in a pond that interfere so that in some places, the waves are higher, and in other places, there's almost no wave. The section to watch is between 4:33 and 5:17. | An important property of waves (radio, sound, water, quantum mechanical!, or otherwise) is that they can interfere with one another. Here's a //Veritasium// video showing how light going through two slits can interfere: In some places, the waves add up, in other places, they cancel out. Although not directly about radio waves, we saw in the [[intro#electromagnetic_spectrum |intro]] that light and radio waves are in fact on the same electromagnetic spectrum. |
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| {{ youtube>Iuv6hY6zsd0 }} | {{ youtube>Iuv6hY6zsd0 }} |
| ====== Wave Addition ====== | ====== Wave Addition ====== |
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| Two waves add up together at every point. Here, the <fc #4682b4>blue</fc> and <fc #008000>green</fc> waves are generated and add up together to form the <fc #ff0000>red</fc> wave. You can move the blue and green waves and see the result. To convince yourself that the red wave is really the sum of the blue and green waves, look at points <fc #4682b4>A</fc>, <fc #008000>B</fc>, and <fc #ff0000>C</fc>. As you move the blue or green wave, you'll see that point <fc #ff0000>C</fc> is always the sum of <fc #4682b4>A</fc> and <fc #008000>B</fc>. | Two waves add up together at every point. Here, the <fc #4682b4>blue</fc> and <fc #008000>green</fc> waves are generated and add up together to form the <fc #ff0000>red</fc> wave. You can move the blue and green waves and see the result. To convince yourself that the red wave is really the sum of the blue and green waves, look at points <fc #4682b4>A</fc>, <fc #008000>B</fc>, and <fc #ff0000>C</fc>. You can move the blue or green waves by sliding their phase (<fc #4682b4>φ</fc> and <fc #008000>Φ</fc>) around. You'll see that point <fc #ff0000>C</fc> is always the sum of <fc #4682b4>A</fc> and <fc #008000>B</fc>. |
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| * the red wave is cancelled out?((Fun fact: This is how [[wp>Active_noise_control |noise cancelling headphones]] work. The headset has a microphone that picks up the noise, inverts the waves, and plays them back in the ear piece. The combination of the real life noise and the inverted noise being played in the speaker cancel out (somewhat).)) | * the red wave is cancelled out?((Fun fact: This is how [[wp>Active_noise_control |noise cancelling headphones]] work. The headset has a microphone that picks up the noise, inverts the waves, and plays them back in the ear piece. The combination of the real life noise and the inverted noise being played in the speaker cancel out (somewhat).)) |
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| If you press the play button on the bottom left corner, you'll see the blue wave travel to the right and the green wave travel to the left. The red wave oscillates up and down but doesn't travel anywhere. This is called a //standing wave//, which we're gonna see later. | If you press the play button on the bottom left corner, you'll see the blue wave travel to the right and the green wave travel to the left. The red wave oscillates up and down but doesn't travel anywhere. This is called a //standing wave//, which we'll see again later when we discuss SWR. |
| ====== Wave Reflection and Multipath ====== | ====== Wave Reflection and Multipath ====== |
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