The speed of light is closely related to how rapidly the electric and
magnetic fields in a light ray change. How rapidly the fields change is also
closely related to how far apart the strong parts of the electric fields are in
the wave. The speed of light is the velocity of electromagnetic waves in vacuum,
which is 300,000 km/sec. Light travels slower in other media, and different
wavelengths travel at different speeds in the same media. When light passes
from one medium to another, it changes speed and direction, a phenomenon called refraction.
Wavelengths are associated
with colors you can and cannot see.
When study waves, you will find that wavelength and frequency are related
by an equation
Speed of the wave = Frequency x Wavelength
When you choose your radio channel, you select the Frequency. The
default value is 90.0 MHz, or 90,000,000 waves per second - for an FM station.
When you choose an AM station, the default frequency is 100.0 kHz, or 100,000
waves per second.
For radio waves or light waves, the Speed of the wave is the speed
of light. In the United States, we often think of that as 186,000 miles per
second. That's as fast as anything can go - according to Einstein's theory of
relativity - which is based on Maxwell's equations for electricity and
magnetism. In other countries (or when scientists use this equation), they
think of the speed of light as 299,792,458 meters per second. The speed of
light is the same whether we use miles per second or meters per second - only
the number is different.
We use the equation to find the Wavelength - we just rearrange it
so that the Wavelength is on the left
Wavelength = Speed of the wave / Frequency
Because the numbers are so big, doing this calculation by hand is a lot of
work. If you were going to do it that way, you would have to solve the
299,792,458 / 90,000,000
Even scientists get tired of doing that kind of problem by hand. That's why
they use computers. A simple computer program to compute wavelength from
frequency is demonstrated below. The
instructions for this program are
A Simple Conversion Tool for Wavelength