dramatic irony occurs when a character on stage is not aware of something the audience or reader knows to be true. in act 5 scene 3 of romeo and juliet why are the following lines of romeo and juliet,why are the following lines of romeo dramatically ironic

Death, that hath sucked the honey of thy breath, Hath had no power yet upon thy beauty. Thou art not conquered. Beauty's ensign yet Is crimson in thy lips and in thy cheeks, And deaths pale flag is not advanced there.