Isn't there a law in business stating that an employer can not loudly reprimand an employee in front of coworkers and ustomers?

I work in a store. I didn't understand something and the boss starting yelling at me (at the front of the store) so loudly that the boy at the back counter heard him.. so did every customer in the store. This isn't the first time he has done this and I'm not the only employee he's treated in this manner.