Rates of Radioactive Decay (Section)
Some watch dials are coated with a phosphor, like ZnS, and a polymer in which some of the 1H atoms have been replaced by 3H atoms, tritium. The phosphor emits light when struck by the beta particle from the tritium decay, causing the dials to glow in the dark. The half-life of tritium is 12.3 yr. If the light given off is assumed to be directly proportional to the amount of tritium, by how much will a dial be dimmed in a watch that is 50 yr old?
Week Two – CH 101 Ch. 1 – Atoms (continued) Current Understanding of the Structure of Matter: o Early Ideas: i. Nothing exists except atoms and empty space 1. Atoms exist in different shapes and move randomly through empty space ii. Matter has no smallest parts 1. Different substances are composed of various proportions of fire, air, earth, and water. iii. Dalton’s Atomic Theory of Matter (and ideas) Supported early idea #1 and led to the Modern Atomic theory and laws: o Law of Conservation of Mass