Troubles with using your speed light (off camera flash)?

Who has troubles using their speed light (also known as off camera flash)? I did for the longest time until I learned what settings I had to use in order for it to work right. Yep, you have to at least have your shutter speed at 1/125 of a sec and no faster then 1/250 of a sec.  The slower your shutter speed is the more lines you will have in your image. The faster your shutter speed is, it will make your image come out with half of it black, mostly on the bottom half. Why you ask? Because when you have your shutter speed set faster then 1/250 of a sec it is only capturing half of the light  that the speed light is shooting off. Meaning that your shutter is taking a photo faster then the light. The light can not travel as fast as your camera is shooting. Don't believe me, no worries I didn't believe the person who told me till I tried it out. So set your shutter speed round 1/500 a sec and take a photo then take one at 1/60 of sec. What did you get? You can post your results in the comment area down below this post. I alway leave my shutter speed at 1/125 of a sec when using my speed light and for the other 2 setting (F-stop, ISO) I can do what I want with them to make my image look good.

Here is what it will look like at the different shutter speeds. I thought I needed to add images so you can see what the speed light will do at the different speeds. (Images are unedited)

                                                                          1/125 of a sec

                                                     
                                                                          1/500 of a sec

                                             

1/1000 of a sec