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Wavelength and frequency of electromagnetic waves

19 January, 2016 - 14:56

We’ll cover several characteristics of electromagnetic waves in this course, such as the relationship between wavelength and frequency, radiation pattern, the direction and different ways of propagation, and so forth.

In fact, you have probably already encountered some basic properties of electromagnetic waves. If you are familiar with them already, this section will be very easy for you. It provides a quick overview of the simplest and most important properties — wavelength and frequency. The other properties will be discussed in Unit 7 of ELEC S211.

Let’s consider a continuous sinusoidal waveform as shown in Figure 1.3. The term period refers to the time difference between two adjacent peaks, or between the same points on any adjacent wave cycles.

Figure 1.3 The timing diagram of a sinusoidal waveform

For a repetitive (or periodic) signal, the term frequency refers to the number of cycles per second. The unit of frequency is Hertz (Hz).

Recall the basic laws of physics: the relationship between frequency and wavelength is given by:

Electromagnetic waves travel at the speed of light in a vacuum — that is, 3 x 108m/s — and the speed of light is denoted by the symbol c. In other media, the velocity will be slowed down by the characteristics of the material that makes up the medium.

Let's take a look at Example 1, in which we calculate the wavelength for a signal with given frequency and velocity.

You should now be ready to undertake the Self-test 1 in this module. While Suggested answers to Self-test 1 are provided below, you should always try to answer the questions on your own first. If you can’t answer a particular question, this shows that you most likely need to review some of the material that you’ve worked through so far.