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 = 1.38, 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?
air-soap
at neither interface
soap-air
at both interfaces
omit
Question 2
What is the wavelength of blue, 480-nm light as it travels through the film?
662 nm
480 nm
348 nm
omit
Question 3
At what minimum non-zero thickness of the film will the intensity of the blue light reflected back into the air be a maximum?
240 nm
87 nm
120 nm
174 nm
omit
Question 4
At what minimum non-zero thickness of the film will the intensity of the same blue light reflected back into the air be a minimum, or experience destructive interference?
87 nm
120 nm
174 nm
240 nm
omit
Question 5
In general, when blue light is removed from white light, the soap bubble would appear to be which color?
grey
yellow
magneta
cyan
omit
Question 6
What is the frequency of the blue light as it travels through the soap film?
8.63 x 10
-4
hz
4.53 x 10
14
hz
6.25 x 10
14
hz
1.04 x 10
20
hz
omit
Question 7
If the soap film were instead specified to be 609 nanometers thick, which wavelength in the visible spectrum would be canceled?
1.22 x 10
3
nm
8.83 x 10
2
nm
1.68 x 10
3
nm
4.2 x 10
2
nm
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