As the distance between two point charges is tripled, the electrostatic force between the charges will become
a) 9 times as great
b) 1/9 as great
c) 1/3 as great
d) 3 times as great

Waves are used in many practical applications to support work, entertainment, and health. one example is the use of ultrasound imaging to safely track the development of a growing fetus. what is a specific example of a practical application of waves in medicine, entertainment, safety, or other fields? provide a brief explanation of how the properties of waves are useful to that application.