What wavelength monochromatic source in the visible region (390 to 710 nm)can be used to constructively reflect off a soap film (n = 1.46)if the film is 222 nm thick?
A) 432 nm
B) 410 nm
C) 473 nm
D) 482 nm
E) 436 nm

Question

What wavelength monochromatic source in the visible region (390 to 710 nm)can be used to constructively reflect off a soap film (n = 1.46)if the film is 222 nm thick?
A) 432 nm
B) 410 nm
C) 473 nm
D) 482 nm
E) ​436 nm

Quizplus · Accepted Answer

Constructive interference occurs when the path length difference between two waves is an integer multiple of the wavelength. In this case, the path length difference is twice the thickness of the soap film, or 444 nm. The wavelength of the light must therefore be an integer multiple of 444 nm. The only wavelength in the visible region that is an integer multiple of 444 nm is 432 nm.

What Wavelength Monochromatic Source in the Visible Region (390 to 710