Destructive interference occurs when the resultant wave is:

• A. The resultant wave is smaller.
• B. The resultant wave is larger.
• C. The frequency doubles.
• D. Wavelength halves.

Answer: (A)

Destructive interference arises when two waves meet out of phase and subtract in amplitude, so the resultant wave is smaller. If the two waves have equal amplitudes and are exactly opposite in phase, they can cancel completely, giving zero amplitude at that point. If the amplitudes aren’t equal, you still get a reduced resultant amplitude equal to the difference between the two. The frequency and wavelength of the resultant wave stay tied to the original waves and the medium; interference changes how much the waves reinforce or cancel at each point in space, not the oscillation rate itself. Therefore, the description that the resultant wave is smaller best captures what destructive interference does.