## television

Television broadcasts also use radio waves (see Figure 1.2). For TV broadcasts, sounds are encoded with frequency modulation, and pictures are encoded with amplitude modulation. The encoded waves are broadcast from a TV tower. When the waves are received by television sets, they are decoded and changed back to sounds and pictures.

## a spectrum of waves

Electromagnetic waves consist of vibrating electric and magnetic fields. They transfer energy across space as well as through matter. Electromagnetic waves vary in their wavelengths and frequencies, and higher-frequency waves have more energy. The full range of wavelengths of electromagnetic waves is called the electromagnetic spectrum. It is outlined in the following Figure 1.1.

Electromagnetic waves on the left side of the Figure 1.1 are called radio waves. Radio waves are electromagnetic waves with the longest wavelengths. They may have wavelengths longer than a soccer field. They are also the electromagnetic waves with the lowest frequencies. With their low frequencies, they have the least energy of all electromagnetic waves. Nonetheless, radio waves are very useful. They are used for radio and television broadcasts and many other purposes. Click image to the left or use the URL below. URL: Q: Based on the electromagnetic spectrum Figure 1.1, what is the range of frequencies of radio waves? A: The range of frequencies of radio waves is between 105 and 1012 Hz, or waves per second.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

electromagnetic waves vary in their wavelengths and frequencies.

``````-->  a. true

b. false
``````

radio waves have the highest frequencies of all electromagnetic waves.

``````a. true

-->  b. false
``````

radio waves have the least energy of all electromagnetic waves.

``````-->  a. true

b. false
``````

radio waves vary in frequency from

``````-->  a) 105 to 1012 hz.

b) 1050 to 10,120 hz.

c) 10,500 to 101,200 hz.

d) none of the above
``````

``````a) have longer wavelengths than fm radio waves.

b) are encoded with signals by changing their amplitude.

c) reflect off the ionosphere.

-->  d) all of the above.
``````

``````-->  a) radio waves carry both sound and picture signals.