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
air-soap
at both interfaces
at neither interface
omit
Question 2
What is the wavelength of red, 729-nm light as it travels through the film?
984 nm
540 nm
729 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?
365 nm
182 nm
270 nm
135 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?
270 nm
365 nm
135 nm
182 nm
omit
Question 5
In general, when red light is removed from white light, the soap bubble would appear to be which color?
grey
magneta
yellow
cyan
omit
Question 6
What is the frequency of the red light as it travels through the soap film?
5.56 x 10
-4
hz
1.62 x 10
20
hz
4.12 x 10
14
hz
3.05 x 10
14
hz
omit
Question 7
If the soap film were instead specified to be 611 nanometers thick, which wavelength in the visible spectrum would be canceled?
9.05 x 10
2
nm
1.65 x 10
3
nm
4.12 x 10
2
nm
1.22 x 10
3
nm
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