The 1st scene happens in the middle of the night, on the dark and windy castle wall. The guards are freezing with cold and trembling with fear, as there's a Ghost who appears and wants to say something.
On the other hand, the 2nd scene happens at court, where all the courtiers are present, along with the queen and the new king Claudius. Although the former king has recently passed out (or murdered, as the reader will find out later), everybody is serene and optimistic. Only the melancholic prince Hamlet is missing.
The two settings are juxtaposed with a context that binds them together (adding to the contrast, at the same time): everybody is well aware of the strange and sudden circumstances of the old king's death. The 1st scene is spooky because of his Ghost who seeks young Hamlet. The 2nd scene leaves a bitter taste because his funeral has been followed by a wedding all too soon.