Which radioactive isotopes did the curies discover?

polonium and radium
radium and carbon-14
carbon-14 and uranium
uranium and polonium

What are similarities and differences of reflection, refraction, diffraction and absorption?

Why don't you see your reflection in water with waves or repples

Which graph represents motion with an object with positive velocity that is located at a position of 3 meters at a time of 0 seconds? a) a b) bb eliminate c) c d) d