The Prestidigitation Approximation

The Prestidigitation Approximation is the eighteenth episode of the fourth season of The Big Bang Theory.

Plot Summary
Priya feels threatened by Leonard  hanging out with his ex-girlfriend Penny  all the time. Sheldon attempts to unravel Howard's  magic trick.

Extended Plot
Leonard and Priya  are in bed together, Priya  urges him to get contact lens as she claims he has beautiful eyes. Later at the Cafeteria, Howard offers to show Raj  a magic trick, Sheldon intervenes and tells him he shouldn't be wasting his time with such trivial matters. Howard performs the tricks anyway and impresses both Raj  and Sheldon. Although Sheldon mocks the trick he is still keen to unravel it. Leonard comes in with his new contact lens which is clearly incompatible with him. Later at the apartment Howard  impresses Penny  with his magic trick, Leonard  comes back from shopping for more grown-up clothes with Priya, the two head for his room. Priya feels uncomfortable with Leonard  hanging out with Penny  all the time and asks him to terminate their relationship, He reluctantly agrees. Howard continually impresses his friends with the magic trick, and Penny successfully solves the magic trick which further crushes Sheldon's ego. Leonard meets Penny  at the Laundry room where she saves Leonard's  silk shirt which he was about to wash in the washing machine. Leonard sees how important Penny is to himself, but he still cuts their relationship with Penny  but in a manner where she doesn't understand. Leonard told Priya  he has cut his relationship with Penny. The next day, Sheldon has grown obsessed with solving Howard's magic trick and has even gone as far as hacking into an Oak Ridge National Laboratory Cray supercomputer to analyze shuffling patterns and procuring Uranium-235 after wondering if Howard used a radioactive tracer. Priya has been offered a job in Los Angeles, Leonard is happy and urges her to relocate to Los Angeles. At the Cafeteria, Sheldon claims he has solved and improved Howard's  magic trick, but it turns out he has bar coded all the cards and used a reader to identify it. Howard feels that Sheldon's  execution was pathetic and shows the trick again, but this time it is revealed to the audience that Raj is just playing along with Howard's  wild guesses. Later, Leonard musters the courage to cut his tie with Penny, she understands that this is because of Priya  so she compromises. Sheldon is depressed that he is unable to solve the magic trick, Howard offers to show it again, this time Sheldon  requests Howard  try it on him. Howard agrees and with Raj's  help he is able to guess Sheldon's  card.

Trivia

 * Leonard tried to use contacts in the 7th grade
 * Leonard was his school's debate club president
 * Leonard has two Star Trek uniforms. Raj has a Lieutenant Uhara uniform, which Priya and her family are embarrassed to know.
 * Leonard can hear Penny's toilet flush from his apartment.
 * This is the first time we see the Tandori Palace which has been referenced before.