How does the frequency and wavelength of a radio wave compare to other waves?

Answer 1

Frequencies and wavelengths are best described by looking at ripples on a pond. The wavelength is the distance between ripples, and the frequency is how many ripples go by a given spot in a second. If you can imagine holding something and splashing it into the water, you can make patterns in the ripples. For example, splashing for a second, being quiet for a second, then splashing for another second could be a code for something. By varying your codes, you can put all kinds of information in the ripples. The thing is, you can't splash faster than the ripples will go out across the water. Basically, you can't carry information that varies any more than about half of the frequency of the wave you are sending it on (this is called Nyquist's theorem). This is what limits how much information can be sent on a given frequency.

If you vary how big you make the ripples, this is called Amplitude Modulation, or AM. If you vary how fast you make the ripples, this is called Frequency Modulation. You've probably heard of these terms before, since radio bands have been specifically set aside for voice transmissions using these methods, and the radio bands have over the years taken on the name of the type of modulation used. There's nothing particularly special about the type of modulation though. You could easily use FM modulation on frequencies that we would consider to be in the AM band. It's just that the FCC has restricted those bands to using only those types of signals. Your television, for example, uses FM to carry the voice and AM to carry the picture.

Most of the things you mention are just variations on how to encode data onto radio waves. It's all the same thing. The FCC sets up various bands of frequencies that you can use for certain things, so that all of the different things agree and can talk to each other. A radio built in the US might not work at all in other areas of the world, because their radio stations aren't governed by the FCC and might have different frequencies assigned to them.

This web site: http://www.ntia.doc.gov/osmhome/allochrt.pdf (warning, PDF file) has the frequency allocations for the United States. Other parts of the world will be different.

The one thing you mentioned that is slightly different is a cordless keyboard. These use infra-red light. It's still the same thing. Infra-red light, just like visible light, is just another frequency of electromagnetic radiation, just like radio waves and x-rays. Your TV remote control also uses infra-red light. It's still exactly the same thing, the signal you want to transmit is encoded onto the light, the same way that signals are encoded onto radio waves.

Most of the frequencies that we can do anything useful with have been allocated for something, so if you come out with some new whiz bang device (like say digital radio) then the FCC may have to change some of its frequency allocations to let it be commonly used by the public.

Answer 2

"Radio" is the label generally given to anything below 300 GHz.

Answer 3

The number of cycles a wave is doing per second.

Answer 4

Divide 300 by the frequency in Megahertz to get the wavelength in metres. the 300 comes from the constant 300,000,000 m/second which is the speed of light (and radio waves).

Answer 5

They are the same.

The frequency you set on your radio dial is the frequency of the waves transmitted from the radio station's antenna.

Answer 6

Radio waves, including microwaves, have longer wavelength and lower frequency

than heat, infra-red, visible light, ultraviolet, x-rays, and gamma rays.