The light reflected from a soap bubble (n = 1.40) appears red (λ = 640 nm) at its center. What is the minimum thickness (in nm)?
A) 124
B) 104
C) 114
D) 134
E) 234

Question

Quizplus · Accepted Answer

The minimum thickness of a soap bubble can be found using the formula:
2nt = mλ
Where n is the refractive index, t is the thickness, m is an integer (1, 2, 3, etc.), and λ is the wavelength of the light.
In this case, n = 1.40, λ = 640 nm, and m = 1 (since we are looking for the minimum thickness).
Substituting these values into the formula gives:
2(1.40)t = 1(640)
Simplifying this equation gives:
t = 114 nm
Therefore, the minimum thickness of the soap bubble is 114 nm, and the answer is choice C.

The Light Reflected from a Soap Bubble (N = 1