I know it's illegal to use an amplifier on a CB radio. I am just
trying to find out this information.

CB is the 11 meter band. With amplifiers being illegal to use on a
CB, it seems that advertising and selling 11 meter amplifiers could
tend to get someone in trouble. However, I was listening to a guy on
the CB and he said he was a trucker and was using a 10 meter
amplifier. I tend not to believe what I hear on the CB but this guy
was definately running some sort of power amp, because he was burying
my needle for many miles, and going opposite directions.

Is it possible to use a 10 meter amp on a CB? Does it need
modifications? (what?), or not?

One other thing. I understand that increasing a 4watt CB to say 10
watts is actually an insignificant gain, but going to 40 watts doubles
the power. How can a 10X increase only double the power? Wouldn't it
be 10 times as much? I dont understand this.
Just curious....

Thanks

Paul