An astronomical source emits radio waves with a frequency of 450 MHz. a. If earth is 20 light years from the source, and we measure an intensity of 8.5 x 10-10 W/m2 here on earth, what is the power of the source? b. What is the amplitude of the electric field of the wave at our location?

Which of the following changes will increase the capacitance of a parallel-plate capacitor? (there could be more than one correct choice.) a) increase the charge on the plates b) decrease the poten5al between the plates c) increase the potential between the plates d) introduce a dielectric material between the plates e) decrease the separation between the plates