Electromagnetic wave is used to transmit signal between mobile phones, and the propagation speed of the signal is______ M / s, the electromagnetic wave length of a radio station is 3M, then its frequency is______ MHz．

Electromagnetic wave is used to transmit signal between mobile phones, and the propagation speed of the signal is______ M / s, the electromagnetic wave length of a radio station is 3M, then its frequency is______ MHz．

Because electromagnetic wave is used to transmit signal between mobile phones, the propagation speed of mobile phone signal is the propagation speed of electromagnetic wave, which is 3 × 108m / s. from the formula C = λ F, we can get that f = C λ = 3 × 108m / S3M = 3 × 108hz = 100MHz. So the answer is: 3 × 108; 100

What are the four parts of the whole electromagnetic wave transmitting device for transmitting sound signals

Power supply - sound signal sensor (MIC) - low frequency amplifying circuit - oscillation circuit - modulation circuit - high frequency amplifying circuit (transmitting circuit) this constitutes a complete system. If you want to talk about the four parts of the transmitting device, that is
1. Low frequency amplification circuit 2. Oscillation circuit 3. Modulation circuit 4. High frequency amplification circuit

The orbit of a planet and the earth around the sun can be regarded as a circle. Every n years, the planet will move to the extension line of the sun earth line, as shown in the figure. The ratio of the radius of revolution of the planet and the earth is___ ．

A. B, C, D: it can be seen from the figure that the orbit radius of the planet is large, so the period is long according to the third law of Kepler. Every n years, the planet will run to the extension line of the sun earth line, which means that from the initial extension line of the sun earth line, the earth will turn one nth more than the planet in front of the planet every year, and after n years, the earth will turn n circles, one more than the planet, that is to say So the period of the planet is nn-1 years. According to Kepler's third law, there is r ground 3R line 3 = t ground 2T line 2, that is: R ground = 3T ground 2T line 2 = (nn-1) 23, so the answer is: (nn-1) 23