CBS has announced the details of the 10th episode of the season, The Athens Recurrence, which will air December 7th.

“The Athens Recurrence” – Sheldon attempts to help Penny understand Leonard’s work, and Wolowitz becomes jealous when Leonard starts hanging out with his new girlfriend, on THE BIG BANG THEORY, Monday, Dec. 7 (9:30-10:00 PM, ET/PT) on the CBS Television Network.

Source: http://the-big-bang-theory.com/