Practice Problems
Thin Film Interference Soap Bubbles
Directions:
On this worksheet you will be investigating the basic properties of
thin film interference
in a soap bubble.
omit
Question 1
A thin soap bubble, n = 1.35, is filled with air. Since the medium outside the bubble is also air, at which of the interfaces (air-soap and soap-air) would the light undergo a 180° phase change upon reflection?
soap-air
at neither interface
air-soap
at both interfaces
omit
Question 2
What is the wavelength of red, 639-nm light as it travels through the film?
863 nm
639 nm
473 nm
omit
Question 3
At what minimum non-zero thickness of the film will the intensity of the red light reflected back into the air be a maximum?
118 nm
160 nm
237 nm
320 nm
omit
Question 4
At what minimum non-zero thickness of the film will the intensity of the same red light reflected back into the air be a minimum, or experience destructive interference?
237 nm
320 nm
118 nm
160 nm
omit
Question 5
In general, when red light is removed from white light, the soap bubble would appear to be which color?
yellow
cyan
grey
magneta
omit
Question 6
What is the frequency of the red light as it travels through the soap film?
1.42 x 10
20
hz
4.69 x 10
14
hz
6.34 x 10
-4
hz
3.48 x 10
14
hz
omit
Question 7
If the soap film were instead specified to be 598 nanometers thick, which wavelength in the visible spectrum would be canceled?
8.86 x 10
2
nm
1.61 x 10
3
nm
1.2 x 10
3
nm
4.04 x 10
2
nm
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