What is the result of two waves interfering out of phase?

• A. Constructive interference
• B. Standing waves
• C. Decreased amplitude
• D. Phase shift

Answer: (C)

When two waves interfere out of phase, they align such that the peak of one wave coincides with the trough of the other. This alignment results in the waves canceling each other out to some extent, leading to a reduction in the resultant amplitude. This phenomenon is referred to as destructive interference. When the two waves completely cancel each other, the amplitude can even drop to zero.

The other options do not describe the effect of out-of-phase interference correctly. Constructive interference occurs when waves align in phase, resulting in an increase in amplitude. Standing waves are formed by the interference of two waves traveling in opposite directions but are usually not characterized solely by out-of-phase interactions. A phase shift refers to a change in the phase angle of a wave, which does not necessarily correlate directly with the cancellation or reduction of amplitude observed in out-of-phase interference.