Applying Physics to Communications Technology

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  • 0:02 Why Humans Communicate
  • 1:17 Analog Signals &…
  • 2:53 Digital Signals & Electrons
  • 5:59 Lesson Summary
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Lesson Transcript
Instructor: David Wood

David has taught Honors Physics, AP Physics, IB Physics and general science courses. He has a Masters in Education, and a Bachelors in Physics.

Learn how physics has led to incredible communication technology, including satellites, fiber optics, computers, and the Internet. See how much you know by taking a quiz.

Why Humans Communicate

Humans are all about communication. We communicate with our families. We communicate with our coworkers. We communicate with strangers. The communities we develop could not have been sustained without good communication. And today, where the entire world is connected, communication continues to be vital. But in order to communicate over huge distances at different times of the day and night, we need some tricks up our sleeves.

Understanding physics is so integral to those tricks that really there is no example of communication technology that isn't an application of physics. After all, physics is the science concerned with the nature and properties of energy and matter; it attempts to explain everything in the universe. The telephone was an application of physics. Going back further, so was the telegraph.

But for this lesson, we'll focus on some modern communications technologies and their origins in physics. To send a communication from one place to another, a signal (or data) must pass between the locations. There are two main types of signals: analog and digital.

Analog Signals & Electromagnetic Waves

An analog signal in physics is just a wave. There are lots of types of waves, but for communication most of the important ones are part of the electromagnetic spectrum. The electromagnetic spectrum includes light, radio waves, microwaves, infrared, ultraviolet, x-rays and gamma rays.

An example of sending analog communication would be satellite communication. Satellites are artificial objects in orbit around the planet, like the earth. We use satellites for many things, but communication is probably the most common. One of the first uses of a satellite was when the president of the United States was able to broadcast a Christmas message in 1958 - the first message to be transmitted via space. Today, communication satellites are used to transmit messages across the whole world for businesses, between world leaders, for news reports and even phone calls and Internet connections.

The signals satellites send are radio waves. Those radio waves are used to send our communications into space, and then the satellites transmit them back down to the earth, again as radio waves. The pattern of the wave represents the exact audio being transmitted. A large peak might be a loud sound, for example, and a small one a quiet sound. But the computers that send and receive those signals are not analog - they're digital. And the physics of digital signals is quite different.

Digital Signals & Electrons

The computers used to send and receive the signals work on physics principles; they turn analog radio waves into digital signals represented by electrons whizzing along circuit boards. Digital signals contain a series of ones and zeros, otherwise known as binary. Computers understand this language perfectly. The electric current (flow of electrons) varies to represent these ones and zeros.

But just to confuse things, digital signals can also be sent using electromagnetic radiation. This is usually done through a communication technology called fiber optics.

Fiber optic cables are cables containing translucent materials called optical fibers that can carry electromagnetic waves - usually infrared. That infrared light reflects off the sides of the cable to continue down the length until it reaches its destination. These signals are digital, just like the electrons: a pulse of light represents a one and the absence of a pulse represents zero. Computers can receive these pulses and make sense of them.

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