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 = 1.34, 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?
at both interfaces
soap-air
air-soap
at neither interface
omit
Question 2
What is the wavelength of green, 492-nm light as it travels through the film?
492 nm
367 nm
659 nm
omit
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?
246 nm
92 nm
123 nm
184 nm
omit
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?
246 nm
123 nm
184 nm
92 nm
omit
Question 5
In general, when green light is removed from white light, the soap bubble would appear to be which color?
cyan
yellow
grey
magenta
omit
Question 6
What is the frequency of the green light as it travels through the soap film?
1.1 x 10
20
hz
4.55 x 10
14
hz
8.17 x 10
-4
hz
6.1 x 10
14
hz
omit
Question 7
If the soap film were instead specified to be 602 nanometers thick, which wavelength in the visible spectrum would be canceled?
1.61 x 10
3
nm
4.03 x 10
2
nm
8.99 x 10
2
nm
1.2 x 10
3
nm
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