Contents
What are the rules of thumb for the electromagnetic spectrum?
By the end of this section, you will be able to: List three “rules of thumb” that apply to the different frequencies along the electromagnetic spectrum. Explain why the higher the frequency, the shorter the wavelength of an electromagnetic wave.
Which is the lowest frequency in the electromagnetic spectrum?
Any electromagnetic wave produced by currents in wires is classified as a radio wave, the lowest frequency electromagnetic waves. Radio waves are divided into many types, depending on their applications, ranging up to microwaves at their highest frequencies.
How is the speed of light related to an electromagnetic wave?
As noted before, an electromagnetic wave has a frequency and a wavelength associated with it and travels at the speed of light, or c. The relationship among these wave characteristics can be described by vW = fλ, where vW is the propagation speed of the wave, f is the frequency, and λ is the wavelength.
Is the electromagnetic spectrum the same as visible light?
We normally associate these properties with visible light, but they do apply to all electromagnetic waves. What is not obvious is that something that is transparent to light may be opaque at other frequencies. For example, ordinary glass is transparent to visible light but largely opaque to ultraviolet radiation.
How are radio bands different from the visible spectrum?
1 For clarity the bands are not shown with uniform frequency or wavelength spacing 2 The visible spectrum occupies only a very small part of the total EM spectrum 3 Bands also have subdivisions (this is particularly true of the radio spectrum) 4 The band divisions are not as sharp as shown, but rather fuzzy, merging into one another
Radio waves have many uses—the category is divided into many subcategories, including microwaves and electromagnetic waves used for AM and FM radio, cellular telephones and TV. The lowest commonly encountered radio frequencies are produced by high-voltage AC power transmission lines at frequencies of 50 or 60 Hz.
How are radio waves generated in the electromagnetic spectrum?
Radio waves can be generated by natural sources such as lightning or astronomical phenomena; or by artificial sources such as broadcast radio towers, cell phones, satellites and radar. AM radio waves are used to carry commercial radio signals in the frequency range from 540 to 1600 kHz.