Hamlet 1.5 Discussion: Shall I Couple Hell?

In this video, Hamlet grapples with the origin of a ghost, considering it might be from heaven, earth, or hell. He initially thinks of it as a spirit from heaven, then considers it might be returning from the earthly realm. However, he is troubled by the possibility that it could be from hell, intending harm. Ultimately, Hamlet rejects the notion of a hellish origin with an exclamation of rejection, 'Phi.'

How does Hamlet's perception of the ghost evolve throughout the text?

What is the significance of the exclamation 'Phi' in Hamlet's contemplation?