Question

Longitudinal sound waves cannot propagate through

solids
steam
wet sand
liquids
gases
a vacuum

Answer 1

Longitudinal sound waves can propagate through fluids like liquids and gases due to their ability to transfer pressure variations but cannot travel through a vacuum as there is no medium to carry them.

Step-by-step explanation:

Longitudinal sound waves require a medium through which to propagate. These waves consist of periodic variations in pressure that travel in the form of compressional movements in fluids, such as air and water, and also as longitudinal waves in solids, where particles move back and forth in the same direction as the wave. However, longitudinal waves cannot propagate through a vacuum, as there is no medium to carry the wave's energy.

In contrast, it is important to note that solids can support both longitudinal waves and transverse waves (where particles move perpendicular to the direction of the wave). Liquids and gases, on the other hand, do not support shear stress well, therefore sound waves in these mediums must be longitudinal. Steam, being a gas, and wet sand, which behaves more like a fluid, are mediums through which longitudinal sound waves can travel. Hence, out of the options provided, a vacuum is the only medium through which longitudinal sound waves cannot travel.

Answer 2

A vacuum

Step-by-step explanation:

Sound waves are examples of mechanical waves. Mechanical waves are waves which are transmitted through the vibrations of the particles in a medium.

For example, sound waves in air consist of oscillations of the air particles, which vibrate back and forth (longitudinal wave) along the direction of propagation of the wave itself.

Given this definition of mechanical wave, we see that such a wave cannot propagate if there is no medium, because there are no particles that would oscillate. Therefore, among the choices given, the following one:

a vacuum

represent the only situation in which a sound wave cannot propagate through: in fact, there are no particles in a vacuum, so the oscillations cannot occur. In all other cases, instead, sound waves can propagate.