What is a medium? (in the waves/electromagnetic spectrum)

How do scientists think that gravity affected the formation of our solar system?

Why are people not able to skip a dive to the deepest part of the ocean

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.