[PHYSICS CHEAT SHEET] Unit 1 2007 (2)

Stephen Machet 2007

Nuclear Radiation is radiation emitted from the nucleus of an atom. A Radioisotope is an unstable isotope. The Electron Volt is a unit used to measure small amounts

of energy; 1eV=1.6 ×10-19 J

𝛼: U92238 → Th90

234 + He 24 + energy

𝛽−: 𝑛01 → 𝑃1

1 + 𝑒−10 + energy

𝛾: An excited atom undergoes gamma decay in order to become more stable. Smoke detectors use americanum-241, which has a half life of 432 years. It is produced when plutonium-241 undergoes beta decay. The half life is the time taken for half of a group of unstable nuclei to decay. Carbon-14 is used in carbon dating. A decay chain is the sequence of stages a radioisotope passes through in order to become stable. At each stage, a more stable isotope forms. The chain ends when a stable isotope is formed. Ionising Radiation is high energy radiation that has the ability to change atoms by removing electrons and therefore giving the atom an overall charge. If ionising radiation removes electrons that form part of a bond between atoms in a molecule, the molecule can split. The two pieces have an overall charge and are known as free radicals. The Absorbed dose, measured in gray (Gy), describes the amount of energy absorbed by each kilogram of tissue that is irradiated.

absorbed dose = energy absorbed

mass

Dose equivalent, measured in sievert (Sv), describes the biological effect of radiation that has been absorbed by living tissue. It takes into account the type of radiation absorbed. dose equivalent (Sv) = absorbed dose (Gy) × quality factor

Background radiation is radiation that is always present. It comes from sources such as the sun, space, soil, living organisms, medical procedures and the materials used in buildings (Terristrial and Cosmic). An ion is an atom with an overall charge (+ or -).

1.71 meV=1.7×106eV 1eV=1.6×10-19Joules

1 volt = 1 Joule

1 coulomb

𝐴02

−tt1

2 Where 𝐴 = current amount of the quantity that is being measured; 𝐴0 = original amount of the quantity that is being measured; 𝑡 = time; 𝑡1

2

= half-life.

Neutron Number: Number of Neutrons (ie 8N) Atomic Number: Number of Atoms (ie 8Z) Mass Number: Number of Neucleons There are no stable elements from Polonium-84 on. Charge of Proton: +1.6 x 10-19

Charge of Neutron: 0 Charge of Electron: -1.6 x 10-19

d

103 106 109 1012

mega

- -