I think the answer is a molecule
Spectroscopy because it talks about the study of spectrum of light.
Should be their masses. Because t<span>he strength of the gravitational force between two objects depends on two factors, mass and </span>distance<span>. the force of gravity the masses exert on each other. If one of the masses is doubled, the force of gravity between the objects is doubled. increases, the force of gravity decreases.</span>
