[SOLVED] Interference in Soap films 1. The problem statement, all variables and given/known data The sketch View Figure shows a thin film of soapy water of uniform thickness t and index of refraction n = 1.33 suspended in air. Consider rays 1 and 2 emerging from the film: Ray 1 represents the reflected wave at the air-film interface and ray 2 represents the wave that reflects off the lower surface of the film. Which of the following statements correctly describes rays 1 and 2 and their path difference? Check all that apply. a.Ray 1 undergoes a half-cycle phase shift. Ray 2 does not undergo any phase shift. b.Both rays 1 and 2 undergo a half-cycle phase shift. c.Ray 2 undergoes a half-cycle phase shift. Ray 1 does not undergo any phase shift. d.The path difference between rays 1 and 2 is about t. e.There is no path difference between the two rays. f.The path difference between rays 1 and 2 is about 2t. http://session.masteringphysics.com/problemAsset/1020409/16/1020409.jpg 2. Relevant equations 2nd = (m + 0.5) (lambda) 3. The attempt at a solution I know there is a 180 degree phase change at the first interface and no change at the second. Using my physics textbook it says with thickness d, for case of normal incidence, extra length is 2d. I am still confused at what parts are true.