The relation between wavelength and frequency

Light moves with a speed

c = 3 x 10⁸ m/s.

We denote wavelength by

Frequency is how many complete waves go by per second. We denote frequency by

Frequency is measured in Hertz = Hz = 1/seconds.

If a wave with a wavelength of 2 meters is going by at a speed of 6 meters/second, then 3 complete waves go by in 1 second. That is, the frequency is 6/2 = 3 waves/second, or 3 Hz. (See units ).Thus

For example, radio station KUGN broadcasts at a frequency of 590 KHz. What is the wavelength of the radio waves?

wavelength
= c/frequency
= (3 x 10⁸ m/s)/(590 x 10³ Hz)
= (3 x 10⁸)/(0.590 x 10⁶) m
~ 5 x 10² m
= 500 m.

ASTR 122 course home page

Updated 1 October 2007

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA