SP212/3321&5521
Chapter 35 - Worksheet #2
Question 1: A thin film of soap (n=1.33) is surrounded on both sides by air (n=1.00). (a) What is the
smallest nonzero thickness of the bubble such that light with a 625 nm wavelength will destructively
interfere in the reflection? (b) What is the smallest thickness of the bubble such that light with a
625 nm wavelength will constructively interfere in the reflection?
Question 2: A thin film of acetone (n=1.25) coats a plate of glass (n=1.50). White light is incident
normal to the film. In the reflections, fully destructive interference occurs for 600 nm and fully
constructive interference occurs for 700 nm. What is the smallest possible thickness of the acetone
film? [Hint: make a list of possible thickness to fulfill each of the two conditions, and look for the
thickness in both lists.]
Question 3: One of the mirrors in a Michelson interferometer is moved 0.350 mm and a shift of
785 bright fringes is observed. What is the wavelength of light producing the fringes?