A Level Physics Practice Exam

What is the phase relationship between two points on a stationary wave that are on either side of the rest position?

1. In phase

2. Out of phase by 90 degrees

3. 180 degrees out of phase

4. Completely dependent on frequency

The correct answer is: 180 degrees out of phase

The correct answer indicates that two points on a stationary wave, which are on either side of the rest position, are out of phase by 180 degrees. In a stationary wave, also known as a standing wave, nodes (points of zero amplitude) and antinodes (points of maximum amplitude) are formed. The rest position, or equilibrium position, is where the wave does not displace any part of the medium, and it is located between two nodal points. When you consider two points that are symmetrically placed around the rest position, such as one point above and one point below this line of equilibrium, they are indeed in opposite phases. As one point reaches its maximum positive displacement (the crest), the other will be at its maximum negative displacement (the trough). This corresponds to a phase difference of 180 degrees. The other options do not accurately describe the relationship in this scenario. The concept of being in phase would imply that both points are at the same displacement at the same time, which is not the case here. Being out of phase by 90 degrees would indicate that one point is at a quarter wavelength ahead of the other, which again isn't applicable for these specific points on either side of the rest position. The