Final answer:
The density of a medium causes refraction, which is the bending of waves as they pass from one medium with a certain density to another medium with a different density. The change in wave speed due to the change in density is what results in the wave changing direction.
Step-by-step explanation:
The property of a medium that causes refraction is its density. Refraction is the phenomenon in which waves change their direction or path of propagation when passing from one medium into another medium with a different density. This bending of waves occurs because the speed of the wave changes as it enters the new medium. The density of the medium influences the speed of light or sound through it, thereby affecting the refractive index.
It's important to note that refraction is not caused by the wave frequency, temperature, or elasticity of the medium directly, although these factors can indirectly affect the density and therefore the refractive index.
The speed of sound depends on the properties of the medium, which include factors such as the medium's density, temperature, and elasticity. However, for refraction, it is primarily the change in density that causes the wave to bend.