y=x^1/2
y^2=x
...Which is the inverse graph of y=x^2, so in other words just draw y=x^2, but on its side, concave in the direction of the x-axis, with turning pt. at (0,0).
As no value of x will produce a negative value for y, simply omit anything below the x-axis and that is your graph of y=x^1/2