| Category | Format | Size |
|---|---|---|
| People's Education Edition Ninth Grade Physics Complete Book | pptx | 6 MB |
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware
Description
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware
Enlightenment
Landlines are connected by telephone lines, and information is transmitted through the telephone lines by electricity.
There is no phone line connection between mobile phones. How do they transmit information?
generation of electromagnetic waves
Rapid changes in current in wires can stir up electromagnetic waves in space
Radio stations, television stations and mobile phones can all emit electromagnetic waves
These electromagnetic waves are generated by the rapidly changing current generated by the complex electronic circuits inside them.
The existence of electromagnetic waves
When there is a rapidly changing current somewhere in a conductor or circuit, an electromagnetic oscillation will be generated there, and electromagnetic waves propagating outward will be generated in the surrounding space.
propagation of electromagnetic waves
The propagation of sound requires a medium, and sound cannot be propagated in a vacuum; while the propagation of light does not require a medium, and can propagate in a vacuum.
Do you think: Does the propagation of electromagnetic waves require a medium?
Can you give an example to prove your point?
The propagation of electromagnetic waves is the same as that of light. It does not require a medium and can propagate in a vacuum in all directions.
The propagation speed of electromagnetic waves is equal to the speed of light, which is C =3×108m/s= 3×105km/s in vacuum.
[Lenovo]: What guess can you get from the propagation speed of electromagnetic waves equal to the speed of light?
Light is an electromagnetic wave!
Wave speed, wavelength, frequency
Electromagnetic waves of different frequencies (or different wavelengths) all travel at the same speed
Electromagnetic waves with high frequencies have short wavelengths
The relationship between wave speed, wavelength and frequency is: c = λf
C: Wave speed, 3×108m/s in vacuum or air
λ: wavelength, unit: m
f: frequency, unit: Hz
Class exercises
1. Which statement about electromagnetic waves is correct ( )
A. Electromagnetic waves can only propagate in vacuum.
B. Electromagnetic waves with different wavelengths have different speeds.
C. Electromagnetic waves propagate to distant places in space along a certain direction.
D. The changing current generates electromagnetic waves in the surrounding space.
In-class training: must-do questions
1. Our country is the country with the largest number of mobile phone users in the world. Information is transmitted between mobile phones through _______.
2. The propagation of electromagnetic waves does not require a medium and can propagate in ____. Light waves are also a type of ____.
3. The propagation speed of electromagnetic waves is the same as the speed of light, which is __________.
4. The electromagnetic wave used in radio, television and mobile phones is the part from hundreds of kilohertz to hundreds of megahertz, called __________.
5. Regarding electromagnetic waves, which of the following statements is correct: ( )
A. Electromagnetic waves cannot propagate in vacuum.
B. The propagation speed of electromagnetic waves in the air is 340m/s.
C. Light waves are not electromagnetic waves.
D. Mobile phones use electromagnetic waves to transmit information when communicating.
Classroom testing
1. When there is a current of magnitude or direction _______ in a wire, electromagnetic waves will be generated in the space around it.
2. The propagation speed of electromagnetic waves in vacuum is _______________, which is the fastest speed of material movement in the universe. This speed has a special symbol C. There is the following quantitative relationship ________ between the wavelength λ, frequency ƒ and speed of electromagnetic waves. It can be seen that if the frequency of electromagnetic waves is higher, its wavelength will be ________.
3. Among the three electromagnetic waves, short wave, medium wave and long wave, the one that propagates fastest in vacuum is ( )
A. Short wave B. Medium wave C. Long wave D. As fast
4. Among the three electromagnetic waves, short wave, medium wave and long wave, the frequency is the highest ( )
A. Short wave B. Medium wave C. Long wave D. Same size
5. Among the following household appliances and communication equipment, which ones do not use electromagnetic waves to work: ( )
A.TV B.refrigerator C.mobile phone D.radio
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For more information about the PPT courseware "Transmission of Information in the Ocean of Electromagnetic Waves", please click on the "Transmission of Information ppt Ocean of Electromagnetic Waves" ppt tag.
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 5:
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 5 The propagation of TV signals relies on electromagnetic waves. Mobile phones rely on electromagnetic waves to transmit information. How are electromagnetic waves generated? How do electromagnetic waves propagate? What is the relationship between wavelength, wave speed, and frequency? 1. How are electromagnetic waves...
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 4:
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 4 Teaching Objectives 1. Knowledge and Skills Understand the generation and propagation of electromagnetic waves. Know that light is an electromagnetic wave and the propagation speed of electromagnetic waves in a vacuum. Know the relationship between wavelength, frequency and wave speed. 2. Process and methods..
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 3:
"The Ocean of Electromagnetic Waves" Information Transmission PPT Courseware 3 Electromagnetic Waves and Our Life TV stations use electromagnetic waves to show us wonderful TV programs. Mobile communication devices greatly facilitate our communication. How do electromagnetic waves propagate? The propagation of sound requires...
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Update Time: 2024-07-30
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