"The Wider and Broader Information Road" Information Transmission PPT Courseware 2

Description

"The Wider and Broader Information Road" Information Transmission PPT Courseware 2

teaching objectives

1.Knowledge and skills

Common sense understanding of satellite communications, optical cable communications, and network communications.

2. Emotional attitudes and values

By learning modern communication knowledge, we can understand the convenience brought by science and technology to mankind and improve our interest in science.

1.Microwave communication

Microwave: electromagnetic waves with wavelengths between 10m and 1mm and frequencies between 30MHz and 300,000MHz.

Advantages: high frequency, high efficiency of information transmission, a large number of channels can be opened at the same time, and good penetration.

Disadvantages: The propagation is approximately straight line, cannot propagate along the earth's surface, and the propagation distance on the ground is short.

2.Satellite communications

Satellite communication: A microwave communication method that uses satellites as relay stations. Most communication satellites are geostationary satellites.

Geostationary satellite: A satellite whose orbital period is the same as the Earth's autobiographical period. When viewed from the Earth, it appears to be hanging motionless in the sky.

Advantages: Wide coverage, only three satellites can provide global signal coverage.

Evenly distributing three synchronous communication satellites around the earth will cover almost the entire earth and enable global communications. They are like several space microwave relay stations. The electrical signal received from one ground station is processed and then sent to another or several ground stations. Now through satellite television, when an emergency occurs in one place, people all over the world can see the scene almost immediately.

We already know that the propagation speed of electromagnetic waves is equal to the speed of light. In fact, light is also an electromagnetic wave. Light has a higher frequency compared to electromagnetic waves. If light is used to communicate, this "highway" is faster than shortwave. The "highway" of microwaves is millions or tens of millions times wider. But how to achieve optical communication?

Ordinary light sources contain many different wavelengths (frequencies) of light, making it difficult to use them to carry information. 1960． American scientist Maiman made the world's first ruby ​​laser, which can produce light with a single frequency and highly concentrated direction - laser.

This makes the fantasy of communicating with light come true.

But lasers are used for actual communication, and are not as simple as lighting up a room with a flashlight. Lasers used for communication generally propagate in special pipes-optical fibers.

3. Optical fiber communication

Optical fiber communication: the use of higher frequency light waves for information transmission.

Advantages: high frequency, high efficiency of information transmission, a large number of channels can be opened at the same time, and good penetration.

But ordinary light cannot: divergence, not single

Laser: Single frequency, concentrated direction, can be used to transmit information.

So what is optical fiber?

Consolidation exercises

1. Microwaves are electromagnetic waves with frequencies between ______MHz and ______ MHz. The properties of microwaves are closer to ______. They generally propagate along ______. Microwaves ______ (optional "can" or "cannot") along Diffraction from the earth's surface, so a ______ must be built every ______ km or so to process the incoming signals and then transmit them out to achieve long-distance communication.

2. The development of modern science and technology has enabled people to realize their dream of satellite communications. Satellite communication uses ______ as a relay station for microwave communication.

3. Evenly deploying ____________ satellites over the earth will cover almost the entire earth’s surface, thus achieving

4. In fact, light is also an electromagnetic wave with a higher frequency than microwave, while laser is light with frequency ______ and direction ______.

5. Which of the following statements about geostationary satellites is incorrect ( )

A. The period of rotation of a geostationary satellite around the Earth is the same as the period of the Earth's rotation

B． Geostationary satellites can serve as relay stations for rebroadcasting microwaves

C. The speed of geostationary satellites is the same as the propagation speed of electromagnetic waves

D. In order for television programs from anywhere in the world to be transmitted to the whole world, at least three synchronous satellites are required

6. Which of the following descriptions about the application of laser is incorrect ( )

A. Using lasers to communicate

B． Precise measurements over long distances using lasers

C. Using lasers to process hard materials

D. Using lasers for general indoor lighting

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Update Time: 2024-11-25

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

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