(a) Sound waves travel through air at Earth's surface with a speed of about
350 m/s.  The pitch produced by "Middle C" on a piano has frequency of just
under 250 cycles per second.  What is the wavelength of Middle C?

(b) Visible light has a wavelength of about 550 nanometers (1 m = 10^9 nm).
What is the frequency of a wavelength of visible light?  If light travels in
waves, why don't we see light moving through the sky in waves the way water
waves travel through a pond?