"The Ocean of Electromagnetic Waves" Information Transmission PPT

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"The Ocean of Electromagnetic Waves" Information Transmission PPT

Part One Content: Basic Knowledge Key Points

Knowledge point 1: Generation of electromagnetic waves

1. Electromagnetic waves are caused by rapidly changing electric currents in space.

2. There are many electrical appliances used at home nowadays. Which of the following electrical appliances will emit electromagnetic waves when working (C)

A. Washing machine B. Refrigerator

C. Microwave oven D. Hair dryer

3. When Xiao Ming was watching TV at home, he discovered that as long as his mother used the hair dryer next to the TV, a lot of "snowflakes" would appear on the screen; as soon as the hair dryer stopped, the "snowflakes" would disappear. This is because the TV receives the light produced by the hair dryer (D)

A. Ultrasound B. Infrasound

C. Noise D. Electromagnetic waves

4. Beautiful rainbows often evoke people's yearning for a better life. The "seven colors of light" of the rainbow belong to (B)

A.Water waves B.Electromagnetic waves

C. Infrasound D. Ultrasound

Knowledge point 2: Propagation of electromagnetic waves

5. When astronauts in space work outside the space capsule, they need to talk through radio communication equipment, explaining that the propagation of electromagnetic waves does not require (optional "need" or "no") media; the propagation speed of electromagnetic waves in vacuum is the same as The speed of light is equal (optional "equal" or "unequal").

6. Regarding the propagation of electromagnetic waves, which of the following statements is correct (C)

A. Can only spread in a vacuum

B. Cannot spread in water

C. Can spread in many media

D. Can only spread in the air

7. The picture shows the electromagnetic spectrum. Which of the following statements is wrong (B)

A. Visible light is also an electromagnetic wave

B. Different electromagnetic waves propagate at different speeds in vacuum

C. Infrared rays have a lower frequency than ultraviolet rays

D. The higher the frequency of electromagnetic waves, the shorter the wavelength

8. There are two electromagnetic waves A and B. It is known that the wavelength of A is 4 times that of B, then the ratio of the frequency of A to the frequency of B is (B)

A.1:1 B.1:4

C.4∶1 D.2∶1

Ocean PPT of electromagnetic waves, part 2: improvement of comprehensive capabilities

9. When entering Gulin Huangjing Old Forest Scenic Area in Luzhou City, people kept taking photos. Photos of the scenic area were uploaded to WeChat Moments on their mobile phones. They were transmitted by electromagnetic waves (optional "ultrasonic waves", "infrasound waves" or "electromagnetic waves").

10.WiFi is a technology that allows electronic devices to connect to a wireless local area network (WLAN). It uses electromagnetic waves (optional "electromagnetic waves", "ultrasonic waves" or "infrared") to transmit information.

11. Scientific research shows that radio waves are also a kind of electromagnetic waves, and their propagation speed in vacuum is 3.0×105 km/s.

12. Different TV channels receive electromagnetic waves in different frequency ranges. As shown in the table, the wavelength of the electromagnetic waves received by channel 1 is longer than that of channel 6 (optional "long" or "short").

13. The walkie-talkie is a commonly used communication method in the field. If the frequency of the walkie-talkie is set to 1.5×108 Hz, the wavelength of the electromagnetic wave emitted by the walkie-talkie is 2 m; when Xiao Ming uses the walkie-talkie to talk to Xiaohua who is 3 km away, Xiaohua The information will be received after 1×10-5 seconds.

15. Regarding electromagnetic waves propagating in the air, which of the following statements is correct (B)

A. The lower the frequency, the greater the wave speed

B. The lower the frequency, the longer the wavelength

C. The longer the wavelength, the greater the wave speed

D. The wavelengths of electromagnetic waves are all the same

16. Regarding electromagnetic waves, which of the following statements is correct (C)

A. The speed of electromagnetic waves is equal to the speed of light. Electromagnetic waves are a kind of light.

B. Microwaves, radio waves, and sound waves are not electromagnetic waves.

C. When the light is turned off, electromagnetic waves will be generated in the space around the light.

D. Electromagnetic waves are the propagation of electromagnetic fields in space. They can only propagate in media and cannot propagate in vacuum.

17. In the following examples, electromagnetic waves are used to transmit information (D)

A. "Echo" positioning of bats B. "Voice" communication of elephants

C. "B-ultrasound" examination of human body D. Scan QR code with mobile phone

18. Which of the following phenomena can explain that electromagnetic waves have energy is (A)

A. Microwave ovens can use electromagnetic waves to heat food

B. Electromagnetic waves can propagate in vacuum

C.Watch the Spring Festival Gala live on TV

D. Electromagnetic waves are longitudinal waves in which the directions of the electric field and magnetic field are perpendicular to each other everywhere.

19. The impact of electromagnetic wave radiation on human health has attracted people's attention. Which of the following situations will hardly produce electromagnetic wave radiation on the human body (D)

A.Watching TV B.Answering mobile phone

C. Play computer games D. Use a flashlight

20. Household appliances such as televisions and microwave ovens have brought many conveniences to our lives. The wavelength of electromagnetic waves used by microwave ovens is very short, but it is longer than the wavelength used by TV remote controls. The wavelengths of the following electromagnetic waves are also longer than those used by TV remote controls. The wavelength used is longer (D)

A.γ rays B.Visible light

C. Infrared ray D. Radio wave

21. On September 6, 2017, the sun erupted with the strongest flare in 12 years. When a flare occurs, the possible impact on the earth is (A)

① Radio shortwave communications are interfered with or even interrupted; ② Large-scale auroras are produced in high latitudes; ③ Interference with the earth’s magnetic field and affects navigation systems; ④ Abnormal increase in precipitation in various parts of the world

A.①②③ B.②③④

C.①③④ D.①②④

Ocean PPT of Electromagnetic Waves, Part 3: Expanding Research and Breakthroughs

23. We live in a sea of ​​electromagnetic waves. When it is necessary to prevent electromagnetic wave interference, a metal shell is usually used to separate the electromagnetic waves from the area that needs to be shielded to prevent the electromagnetic waves from entering. This approach is electromagnetic shielding. There is a metal cabin in the China Science and Technology Museum, with a large window on the side inlaid with a piece of electromagnetic shielding glass, as shown in the picture. Please design an experiment with your own equipment to test whether this piece of electromagnetic shielding glass can shield electromagnetic waves. Write down the experimental procedures and judgment methods.

Experimental equipment: two normal mobile phones A and B;

Experimental steps: Place one of the normal mobile phones A inside the electromagnetic shielding glass in the metal cabin, use another normal mobile phone B to call mobile phone A, and listen to whether mobile phone A rings to determine whether mobile phone A receives the incoming call signal;

Judgment method: If mobile phone A in the cabin cannot receive a signal, it means that the electromagnetic shielding glass has a shielding effect; if mobile phone A receives a signal, it means that the electromagnetic shielding glass has no shielding effect.

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Update Time: 2024-11-11

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