Sound is a form of energy that travels through different mediums, including solids, liquids, and gases. When sound waves propagate through these mediums, they can exhibit interesting phenomena such as reflection, refraction, and diffraction.

Reflection occurs when sound waves encounter a boundary and bounce back. A common example of this is when sound waves hit a wall and are reflected back towards the source. The angle of incidence, which is the angle at which the sound waves hit the boundary, is equal to the angle of reflection, the angle at which the sound waves bounce back.

Refraction happens when sound waves encounter a change in the density of a medium, causing them to change direction. This can occur when sound waves pass from one medium to another, such as air to water, or when there are variations in temperature and pressure. For instance, sound waves can bend when passing from warm air to cooler air near the ground, leading to sound being heard over long distances.

Diffraction is the bending and spreading of sound waves as they encounter an obstacle or pass through an opening. When sound waves encounter an obstacle that is comparable in size to their wavelength, they can bend around it and spread out on the other side. This is why we can hear sounds even if there are obstacles blocking our direct line of sight. For example, the sound of a loudspeaker in another room can still be heard because the sound waves can diffract around the doorway.