Refraction is caused by any wave crossing the boundary out of one substance and into another one. The two different substances may be no more than two parcels of air at different temperatures.
Logically both masses will collide and well make a reaction. first of all depending on the small mass it will either merge or unite with the big mass or it will bounce away from it . if this happen it will make a reaction that will affect both masses. Hope this helps if it is incorrect please let me know :)
The properties of the wave don't determine its speed. The properties of the medium do. You can FIND the speed by measuring the wave's frequency and wavelength.
The equation to find force is f=ma. So, if you plug in the information that you have you'll get F=5x3 and that'll equal F=15N
