What is the resultant amplitude when two waves of equal frequency are exactly out of phase?

Conditions

• The two waves have the same frequency.
• The two waves are exactly out of phase (anti-phase).

Reasoning, step by step

1. Identify the amplitudes of the two individual waves.
2. Verify that the waves have the same frequency and are in anti-phase.
3. Calculate the absolute difference between the two amplitudes to find the resultant amplitude.

Example

The video shows a blue wave with amplitude $A=2.5$ and a red wave with amplitude $A=0.5$ in anti-phase. The resulting green composite wave has a reduced amplitude, specifically $|2.5 - 0.5| = 2.0$.

Common misconceptions

• Believing that the waves will completely cancel each other out regardless of their amplitudes.
• Assuming that the resultant amplitude is the sum of the amplitudes.

Watch the explanation

Explore next

• Under what condition will two anti-phase waves completely cancel each other out?
• How does the phase difference affect the resultant amplitude in general?