Two light waves combine and produce a region of darkness. Which of the following must be true in that region?
A) The waves were unpolarized.
B) The waves came from the same source.
C) The waves had different wavelengths.
D) The waves were a half-wavelength out of phase.

Question

Quizplus · Accepted Answer

When two waves combine to produce a region of darkness, it is called destructive interference. This occurs when the waves are exactly half a wavelength out of phase with each other. Therefore, option D is correct. Options A and B are not necessarily true as polarization and source are not directly correlated with interference. Option C is incorrect because if the waves had different wavelengths, they would not be in phase to create interference.

Two Light Waves Combine and Produce a Region of Darkness