A Level Physics Practice Exam

In a standing wave pattern created by ultrasound, what is found at the nodes?

1. Maximum particle displacement

2. Particles are stationary

3. Increase in wave amplitude

4. Particles experience maximum kinetic energy

The correct answer is: Particles are stationary

In a standing wave pattern, nodes are points where there is no displacement of particles as the wave oscillates. At these locations, the waves moving in opposite directions effectively cancel each other out, resulting in a condition where the particles do not move at all. This means that the displacement of particles at the nodes is zero at all times, indicating they are stationary. The other options involve aspects of wave behavior that do not apply at the nodes. For instance, maximum particle displacement occurs at the antinodes, not the nodes. Similarly, kinetic energy reaches its maximum at the antinodes where particles are moving the fastest, rather than at the nodes where motion is non-existent. The idea of an increase in wave amplitude does not pertain to the stationary nature of the particles at the nodes; instead, it is related to the entire standing wave pattern and where energy is concentrated within it. Thus, the correct understanding of nodes directly supports the assertion that particles are stationary at those points in a standing wave pattern.