Speed of electromagnetic wave

The speed of any electromagnetic (or EM) wave is around in a vacuum.

Wavelength and frequency changes

Because of our equation linking wavelength (), frequency () and velocity ():

We can re-arrange it to find the frequency, :

Or, to find the wavelength, :

From this, we can tell that (if velocity remains constant):

• if the wavelength increases -> the frequency will decrease
• if the wavelength decreases -> the frequency will increase

Similarly:

• if the frequency increases -> the wavelength will decrease
• if the frequency decreases -> the wavelength will increase

Again, this only works if velocity remains constant. With an EM wave, the velocity is always constant for any type of electromagnetic wave!