Which of the following is an example of sound refraction?
a).sound waves bouncing off a canyon wall to create an echo
b).reverberations in a concert hall
c).a high pitch sound changing to a low pitch sound
d).sound waves changing direction as they encounter different air temperatures

b).reverberations in a concert hall

Explanation:

Sound refraction occurs when the sound wave leaves one environment for another, causing a different wave refractive index. This passage ends up causing a change in the speed of propagation and a variation in the length of the sound wave. An example of this can be seen when you recognize reverberations in a concert hall.

This phenomenon does not happen only in sound waves, as it can also be observed in light.

chert is a sedimentary rock composed of microcrystalline or cryptocrystalline silica. with this little bit of information, you can come to the conclusion that your answer is c.  

explanation:

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.