Where do radiowaves come from?

Question

Is there somthing that emits radiowaves?

like a devce?
And what waves do cellphones make?

Answer 1

Radio waves are a form of electromagnetic radiation, created whenever a charged object (in normal radio transmission, an electron) accelerates with a frequency that lies in the radio frequency (RF) portion of the electromagnetic spectrum. In radio, this acceleration is caused by an alternating current in an antenna. Radio frequencies occupy the range from a few tens of hertz to three hundred gigahertz, although commercially important uses of radio use only a small part of this spectrum.[1]

Electromagnetic radio spectrum

Other types of electromagnetic radiation, with frequencies above the RF range, are microwave, infrared, visible light, ultraviolet, X-rays and gamma rays. Since the energy of an individual photon of radio frequency is too low to remove an electron from an atom, radio waves are classified as non-ionizing radiation.

Mobile phones and the network they operate under vary significantly from provider to provider, and even from nation to nation. However, all of them communicate through electromagnetic radio waves with a cell site base station

Answer 2

Radiowaves are created when an electric particle (like electron) excercises the acceleration/deceleration. Theoretically the proof can be derived using Maxwell equations. If the electric particle travels uniformly (without acceleration) the particle does not radiate. (You might ask why the electrons rotating around the atomic nucleus - and excercising acceleration - do not radiate. The answer is explained by quantum mechanics and we will leave it there.) In fact due to the energy conservation law, the mechanical energy spent to accelerate/decelerate the particle transforms directly into the energy of elecromagnetic wave. In pratice there is a metal rod called antena into which the electronics pumps the ac sin wave shaped current. The acceleratin/deceleration of the moving electrons in antena causes that antena radiates. The power of radiation (the length of propagation) is proportional to the amplitude of the electric signal as well as to the frequency. That is the reason why all devices use very high frequency called carrier to propagate radio waves to reasonable distances. New cellular phones like GSM work on 1.8 or 1.9 MHz that is enough to get reasonable distance (order of few km in open space) with very small power from the cell phone (about 10 mW).

Answer 3

Radio waves are part of the electromagnetic spectrum and can come from natural and artificial sources.

Natural sources of radio waves, such as the sun or a few forms of nuclear decay produce the waves in an incoherent random form.

Artificial sources of radio waves, such as a transmitter are almost always are encoded with information by one of the following means:
1. Turning the transmitter on and off in patterns such as Morse code.
2. Modulating the frequency (FM) in either analog or digital patterns.
3. Modulating the amplitude (AM) in either analog or digital patterns.

The only examples that I know of where artificial sources of radio waves are not encoded with information are Nuclear detonations, and Tesla Coils. Nuclear detonations produce a pulse of electromagnetic radiation clear across the frequency spectrum including radio waves and Tesla Coils were experimentaly used for wireless power distribution in the late 17th century.

The original radio transmitter (wireless telegraph) consisted of a high voltage oscillator tank circuit driving the primary coil of a resonate transformer with the secondary coil being the base of the transmission antenna. This was a Tesla Coil and was the patented invention of Nikola Tesla that Marconi stole the entire design and called it the radio. All Marconi was doing was turning the Tesla coil on and off with Morse code and the US supreme court eventualy striped Marconi of the pattent for the radio and awarded the radio patent to Tesla six years after Tesla's death.

The modern radio transmitters are very similar in form to the original with the exception of the addition of either frequency or amplitude control circuits on the oscillator tank circuit and they work on much lower voltages.

Cellphones also work on this same principal and produce microwaves, which are identical to radio waves in every way except for the frequency of oscillation. Microwaves are much faster.

Microwave ovens and X-Ray machines also work on this very same principle as well.

Answer 4

The Sun emits radiowaves. So do clouds of gas - molecular hydrogen, for example, or radio lobes in galaxies.

Answer 5

cell phones use microwave
radiowaves means the waves propagating at a frequency called radiofrequency . yes the audio waves superposed on em waves are generated(not naturally emitted) by the devices like transmitters.