Question on Chronicles of Narnia: Prince Caspian the movie?

Okay, I have a question on the Prince Caspian movie. My question is on the scene when the pevensies are in the woods and Lucy first encounters Aslan in a dream, and then goes to find him in real life. Instead, she and Peter find prince Caspian. My question is that in Narnia the pevensies have been gone for 1300 years, so how did Peter know who prince caspian was? They have crossed swords and then Peter stops and goes "Prince Caspian?" How does he know who he is and what he looks like, if they have never met and are from different times?