You are going on a car trip with your family across the United States. To your brother's
surprise, the AM radio station that your family
is listening to is coming from a city 600 miles
away. Explain to him how this is possible. Be
sure to describe how the ionosphere affects AM
radio transmissions.

Which of these is the best way to manage a natural resource

Hydroelectricity provides about 7 percent of the electricity generated in the united states. (a) explain how a hydroelectric power plant converts energy stored in water into electricity. (b) identify two factors that determine the amount of electricity that can be generated by an individual hydroelectricity power plant. (c) describe the two main types of land-based hydroelectric power plants. (d) describe two economic advantages and two environmental disadvantages of hydroelectricity.

The center of the milky way most likely contains a. empty space. b. a red giant star. c. a globular cluster. d. a supermassive black hole.