Based on what you have seen in this gizmo what is the best definition of the doppler effect?

Why doesn't heat added to water make the tempature rise above 100c

Which of the following observations indicates that there is a small, dense, positively charged part in the center of an atom? some uncharged particles are scattered by a gold foil. all uncharged particles are attracted towards a gold foil. all positively charged particles pass straight through a gold foil. some positively charged particles bounce back from a gold foil.

What type of matter is made of only one kind of atom