Rami Arieli: "The Laser Adventure" Chapter 1.1 page 3
Wavelengths Comparison
Figure 1.3 describes how two different waves (with different wavelengths) look at a specific moment in time. Each of these waves can be uniquely described by its wavelength.
Figure 1.3: Short wavelength (l1 ) compared to longer wavelength (l2 )

For electromagnetic waves, this wavelength is related to the type of radiation of the wave.


You can play with an interactive demo of two waves with different wavelengths, to see this differerence. Click on Two Wavelengths Applet