Final answer:
Jocasta encourages Oedipus not to delve into prophecies after Tiresias's departure, likely because she fears the prophecies about Oedipus killing his father and marrying his mother are true, and hopes to protect themselves from the impending tragedy.
Step-by-step explanation:
Oedipus thinks that Jocasta reacts in a particular manner after Tiresias leaves because she does not want Oedipus to investigate the prophecies any further. Jocasta dismisses prophecies, arguing that they are unreliable, as evidenced by her recounting that an oracle had predicted that her son would kill her husband Laius, yet she believed he was actually killed by bandits. However, when Oedipus reveals that he had killed a man at a crossroad and the coincidence with the place of Laius's death, she likely senses the truth behind the predicaments and becomes increasingly worried that the prophecy could be true. Her own experiences and knowledge about Laius's death and Oedipus's potential involvement cause her to want him to stop uncovering more information, possibly to protect him or herself from the painful truth.