1. yes
2. yes, in vacuum
3. yes, wavelength = period x speed
4. yes, frequency = speed/wavelength
5. Aha, tougher question. The speed is different in different media. Since the frequency doesn’t change, the wavelength must change proportional to the speed.
Why doesn’t the frequency change? The wave in the new medium is driven by the fields from the old medium, and they wiggle back and forth with some frequency. So they drive wiggles at that same frequency.
Why does the speed change? That was first understood by Lorentz. The wave drives charged particles into oscillation at its frequency. They re-radiate more waves. It’s tricky, but the sum of the old wave and the new one lags behind where the old wave would have been, in effect moving more slowly.
Mike W.
(published on 10/22/2007)
