Radars can help meteorologists detect clouds and sailors detect submarines. Radars send out radio waves and record their echoes after the radio waves reflect off an object. Two radars send out radio waves with the same frequency. The first radar sends radio waves through the air. The second radar sends radio waves through the ocean. What is true about these radio waves?

Theoretically, which metal should be the most reactive? hydrogen lithium francium fluorine

The picture represents the process that produces most of the energy used by living organisms on earth. which process is represented in the picture? a) the magnetic attraction between two hydrogen nuclei. b) the fusion of hydrogen nuclei to produce a helium nucleus in the core of the sun. c) the fission of hydrogen nuclei to produce a helium nucleus in the core of the sun. d) the chemical reaction between hydrogen nuclei to produce a helium nucleus in earth's atmosphere.

What does a numerical subscript following an element in a chemical formula mean?