"Entering the Information Highway" Entering the Information Age PPT Courseware 2

Description

"Entering the Information Highway" Entering the Information Age PPT Courseware 2

What is the "Information Superhighway"

The information highway refers to a large-capacity, high-speed communication network that can exchange various information.

Modern communication networks consist of optical fiber communication (laser communication), satellite communication, microwave communication, mobile communication and the Internet (network communication), which realize large-capacity and high-speed transmission of information, forming an "information highway".

1. Optical fiber

Optical fiber is referred to as optical fiber.

Optical fiber is a medium for transmitting optical signals.

Lasers are used in fiber optic communications. Not ordinary light. Because the light emitted by ordinary light sources is mixed with light of many frequencies, it is not only difficult to load information, but also has poor communication quality. The laser has high brightness, good monochromaticity and good directivity. The energy is always concentrated in the propagation direction, making it easy to modulate the signal.

The laser in the optical fiber propagates forward in the form of continuous reflection, so the optical cable does not need to be laid in a straight line.

Telephone, television, radio and other signals as well as data files can be transmitted on the "information highway" composed of optical fibers without interfering with each other.

Characteristics of optical fiber:

⑴Large information capacity. Since the frequency of light waves is much higher than the frequency of radio waves, the information capacity carried by light waves is much greater than that of radio waves. One optical fiber can simultaneously transmit an amount of information equivalent to 10,000 telephone lines. On the information highway composed of optical fiber, 500 TV channels can be transmitted simultaneously.

⑵ Fast transmission speed. Because what is transmitted is an optical signal. Optical fiber is by far the fastest transmission medium and can easily reach 1000Mbps.

⑶Long transmission distance. Optical fibers are very thin (as thin as a hair) and have two layers: an inner layer and an inner layer. Light propagates in the inner layer. Therefore, optical fiber has strong anti-interference ability, can reduce signal attenuation, and is suitable for transmitting large amounts of information over long distances.

⑷The frequency band is extremely wide.

⑸Strong anti-interference ability. Light propagates in the inner layer and is not affected by external electromagnetic interference.

⑹Strong confidentiality. Since it transmits light beams, it does not radiate signals outwards, effectively preventing eavesdropping.

⑺Economic. Save metal, not afraid of moisture, not afraid of corrosion, long service life.

2. Modern telecommunications network

Modern communication networks consist of optical fiber communication (laser communication), satellite communication, microwave communication, mobile communication and the Internet (network communication), which realize large-capacity and high-speed transmission of information, forming an "information highway".

Satellite Communications

Global communications can be achieved with 3 communication satellites.

Satellite communications use artificial earth satellites as relay stations. The satellite receives the signal from the ground station, amplifies it, and then forwards it to another ground station.

The communication satellites currently used to forward signals are almost all geostationary satellites or synchronous satellites, that is, the time it takes for a satellite to orbit the earth is exactly equal to the time it takes for the earth to rotate once, and the satellite is stationary relative to the earth station.

Satellite communications can be used for domestic or international communications and can transmit telegraphs, telephones, faxes, televisions, and high-speed data. Satellite communications have the characteristics of wide communication bandwidth, large transmission capacity, large coverage area, and multi-address communication capabilities.

practise

1. The Shanghai People's Broadcasting Station emits an electromagnetic wave at a frequency of 990kHz, and the Central People's Broadcasting Station emits an electromagnetic wave at a frequency of 15.58MHz. The wavelengths of electromagnetic waves they emit should be equal to ______ and ______ respectively.

Analysis: Because the speed of electromagnetic waves of different frequencies in vacuum (or air) is the same, and they are all equal to 3×108m/s. According to wave speed (c) = wavelength (λ) × frequency (ν), so

2. The Shanghai TV studio is broadcasting a live theatrical evening. An audience member is watching 30m away from the actors, while a classmate in Beijing is watching the same program in front of the TV. It is known that the distance from Beijing to Shanghai is 1460km. Whose ear does the sound reach first? Why?

Analysis: Comparison based on the speed of sound and the speed of electromagnetic waves.

3. Because laser energy is highly concentrated in the air, it can be used to measure the distance between the moon and the earth. It is known that the laser beam emitted from the ground is reflected back to the earth by the reflector on the moon, taking a total of 2.563 seconds. Try to calculate the distance between the moon and the earth based on the above data.

Analysis: According to the propagation speed of the laser and the time it takes from the earth to the moon, the distance can be calculated according to the formula of uniform motion.

Solution: It is known that the propagation speed of laser in the air is v=3.0×105km/s, and the time for the laser beam emitted from the ground to reach the moon is

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"Stepping onto the Information Highway" Entering the Information Age PPT Courseware 3:

"Entering the Information Highway" Entering the Information Age PPT Courseware 3 New Knowledge Exploration What is the Information Highway? The Information Highway refers to a large-capacity, high-speed communication network that can exchange various information. Modern communication networks consist of optical fiber communications (laser communications), satellites...

"Stepping onto the Information Highway" Entering the Information Age PPT courseware:

"Entering the Information Highway" Entering the Information Age PPT courseware 1. The information highway refers to the communication network of ________ and ________ that can exchange various information. Signals and data files such as telephone, television, radio, etc. can be transmitted on ________ The information highway that constitutes...

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Update Time: 2024-11-22

This template belongs to Physics courseware Shanghai Science Edition Ninth Grade Physics industry PPT template

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