A Level Physics Practice Exam

In the context of waves, what does the term 'compression' refer to?

1. Increased pressure in a medium

2. Vibration of particles in a liquid

3. Wave reflection off a surface

4. Energy loss due to friction

The correct answer is: Increased pressure in a medium

Compression in the context of waves specifically refers to regions where particles in a medium are pushed closer together, resulting in increased pressure. This phenomenon is characteristic of longitudinal waves, such as sound waves, where the motion of particles in the medium alternates between areas of compression (where particles are densely packed) and rarefaction (where particles are spread apart). When a wave travels through a medium, the energy is transmitted by compressing and decompressing the particles, creating regions of high and low pressure. The other options describe different concepts. The vibration of particles in a liquid pertains more broadly to the general movement of particles, which can occur in multiple types of waves. Wave reflection relates to how waves bounce off surfaces, representing their interaction with boundaries. Energy loss due to friction involves the conversion of wave energy into other forms, such as heat, rather than a direct reference to the characteristics of the wave itself.