The force (attractive if the charges are dissimilar, else repulsive) is along a line that connects the two particles.
This can be viewed as a decrease in the wavelength of the wave. A decrease in wavelength at a constant speed is associated with an increase in frequency since waves follow the equation v=f*λ, where λ is the wavelength and f is the frequency.
Answer:
Kepler did and stated that planets move in a elliptical orbit with the sun in the center.
