The light reflected from a soap bubble (n = 1.40)appears red ($\lambda$ = 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

For a soap bubble, the minimum thickness (t) required to produce constructive interference for red light of wavelength (λ) is given by:

2t = mλ/n

Where m is an integer (1, 2, 3...), and n is the refractive index of the soap bubble.

In this case, we have: 
λ = 640 nm
n = 1.40 
m = 1 (for the first-order maximum at the center of the bubble)

Substituting these values into the above equation gives us:

2t = (1)(640 nm)/(1.40)

Solving for t, we get:

t = 114.3 nm ≈ 114 nm

Therefore, the minimum thickness of the soap bubble is 114 nm, which is closest to option C).

The Light Reflected from a Soap Bubble (N = 1 λ\lambdaλ

The Light Reflected from a Soap Bubble (N = 1 $\lambda$