Wave speed = (wavelength) x (frequency)
We know the wavelength, but we don't know the frequency. How can we find the frequency ? "Here frequency frequency."
We know the period, and frequency is just (1 / period). So . . .
Wave speed = (wavelength) / (period)
Wave speed = (2.1 meters) / (9.4 seconds)
Wave speed = (2.1 / 9.4) m/s
<em>Wave speed = 0.223 m/s</em>
This true it will be visible if they are covered
<span>From the point of view of the astronaut, he travels between planets with a speed of 0.6c. His distance between the planets is less than the other bodies around him and so by applying Lorentz factor, we have 2*</span>√1-0.6² = 1.6 light hours. On the other hand, from the point of view of the other bodies, time for them is slower. For the bodies, they have to wait for about 1/0.6 = 1.67 light hours while for him it is 1/(0.8) = 1.25 light hours. The remaining distance for the astronaut would be 1.67 - 1.25 = 0.42 light hours. And then, light travels in all frames and so the astronaut will see that the flash from the second planet after 0.42 light hours and from the 1.25 light hours is, 1.25 - 0.42 = 0.83 light hours or 49.8 minutes.
The answer must be a mass x velocity
