Storyboard Szöveg
- Csúszik: 1
- good afternoon class, so today were going to talk about scientist and their contribution to the EM waves
- Csúszik: 2
- Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field. In other words, EM waves are composed of oscillating magnetic and electric fields.
- Sir, may I ask what is EM waves?
- Now, let's start our topic
- Csúszik: 3
- About 150 years ago,James Clerk Maxwell, an English scientist, developed a scientific theory to explain electromagnetic waves.He noticed that electrical fields and magnetic fields can couple together to form electromagnetic waves.
- Csúszik: 4
- Sir, how about Heinrich Hertz?
- Csúszik: 5
- Heinrich Hertz, a German physicist, applied Maxwell's theories to the production and reception of radio waves. The unit of frequency of a radio wave -- one cycle per second -- is named the hertz, in honor of Heinrich Hertz.
- With this oscillator, Hertz solved two problems. First, timing Maxwell's waves. He had demonstrated, in the concrete, what Maxwell had only theorized - that the velocity of radio waves was equal to the velocity of light! (This proved that radio waves were a form of light!) Second, Hertz found out how to make the electric and magnetic fields detach themselves from wires and go free as Maxwell's waves.
- Csúszik: 6
- Neither an electrical field (like the static which forms when you rub your feet on a carpet), nor a magnetic field (like the one that holds a magnet onto your refrigerator) will go anywhere by themselves. But, Maxwell discovered that a CHANGING magnetic field will induce a CHANGING electric field and vice-versa.
- That's for today. Goodbye class we will have short quiz tomorrow
- Goodbye sir, see you tomorrow
- Csúszik: 0
- Hertz proved the existence of radio waves in the late 1880s. He used two rods to serve as a receiver and a spark gap as the receiving antennae. Where the waves were picked up, a spark would jump. Hertz showed in his experiments that these signals possessed all of the properties of electromagnetic waves.
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