Monochromatic Light (λ = 500 Nm) Is Incident on a Soap

Multiple Choice

Monochromatic light (λ = 500 nm) is incident on a soap bubble (n = 1.40) . How thick is the bubble (in nm) if destructive interference occurs in the reflected light?

A) 102
B) 179
C) 54
D) 1
E) 89