expression - go on?

Question

in british english is the expression ¨go on ¨ used to express disbelif?

ex :
A : i heard you can get in to harvard med school with just a 3.5 grade point average!
B: go on!!!
A: no, its true. lol

Answer 1

you are correct. it's like saying 'you must be joking!" or "no way!"

Answer 2

It can indeed mean what you say, provided the tone of the voice or the punctuation (!) is correct.
Different punctuation or tone of voice can be a straightforward invitation to the speaker to say more. Then you would write:
A: I heard you can get into Harvard med school with just a 3.5 grade point average ......
B: Go on ---- [as if to say, 'but that can't be all that's needed?']
C: There is nothing more. That's really all you need!
That may well be how the colloquial interpretation came into being.

Answer 3

In English the expression "go on" is equivalent to "get out"

Answer 4

That's correct.
Sometimes they say "Never!"
It's like the USA way of saying "Get out of here" (remember how Seinfeld used to push people when he said that?)
.