How many half lives have passed if a sample contains one sixteenth of its original amount of radioactive material

List four observations that indicate that a chemical reaction may be taking place

What is the correct term for living the most sustainable life you can within your current circumstances?

If we compare and contrast electromagnetic waves with sound waves, all but one statement is true. that is a) sound waves require a medium to travel while electromagnetic waves do not. b) electromagnetic waves can travel through the vacuum of space while sound waves cannot. c) electromagnetic waves must have a medium in which to travel, but sound waves can travel anywhere. eliminate d) sound waves must bounce off of matter in order to travel while electromagnetic waves do not require matter to be present.