Short Answer/Essay Note: Your teacher will grade your responses to questions 19 and 20 to ensure you receive proper credit for your answers.
What is global warming? What can people do to reduce global warming?

Which theory was contradicted by experiments with the photoelectric effect? light spreads out after it passes through a small opening. as soon as light strikes metal, electrons will be ejected. visible light, regardless of color, will cause the ejection of electrons when striking metal. the kinetic energy of ejected electrons depends on the frequency of light that strikes the metal.