PhysicsLAB Practice Problems
Thin Film Interference Glass Coating

Directions: On this worksheet you will be investigating the basic properties of thin film interference.



Question 1  A thin film, n = 1.4, uniformly covers the top of a glass plate, n = 1.51. If the medium above the film is air, at which of the interfaces (air-film and film-glass) does the light undergo a 180° phase change upon reflection?
Question 2  What is the wavelength of green, 572-nm light as it travels through the film?
Question 3  At what minimum non-zero thickness of the film will the intensity of the green light reflected back into the air be a maximum?
Question 4  At what minimum non-zero thickness of the film will the intensity of the same green light reflected back into the air be a minimum, or experience destructive interference?
Question 5  In general, when green light is removed from white light, the film would appear to be which color?
Question 6  What is the frequency of the green light as it travels through the film?
Question 7  If the glass plate is 28 centimeters thick, how many seconds would be required for the transmitted beam to travel through the glass?


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