Physics ATAR - Nuclear Physics notes (year 11) PDF

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Unit 1 Physics ATAR - nuclear physics summary notes...

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PHYSICS CHEAT SHEET Mass Number- A Atomic Number- Z Alpha decay (α)

X

Mass number= nucleons= protons+ neutrons Atomic number= Protons (+ charged) Neutrons (no charge)= mass number-atomic number

(Helium nucleus) Speed: ~0.1C

α

NOTE: In any nuclear reaction, atomic and mass numbers are conserved (stay the same). Energy is released during

When heavy nucleus decays, may eject alpha particle. U→ Th+ α+energy Beta decay (β)

(electron FROM NUCLEUS) ~0.9C

β

NOTE: C=Speed of Light = 3x10^8

Occurs in nuclei (nucleuses) where there is imbalance of neutrons to protons. C→ N+ β + antineutrino Gamma Decay (γ)

γ

(High-frequency electromagnetic radiation; light wave) Speed: 1C

Generally after a radioisotope has emitted α or β, the new nucleus holds excess energy. Protons and neutrons rearrange and release gamma. I→ Xe+ β + γ Isotopes of elements- Atoms with same number of protons but different number of neutrons (same chemical properties). Radioisotope- an unstable isotope that is radioactive. Radioactivity- when an unstable isotope spontaneously emit a particle and then change into a different element or isotope Artificial Transmutation- manufacturing of radioisotopes by bombarding a stable isotope with neutrons. A neutron is absorbed and the atom becomes an unstable isotope. Instability Imbalance of electric force of repulsion between protons, nuclear force of attraction between nucleons (strong force; short range). Detection Geiger counter: radioactive emission enters the tube ionises argon gas and causes a pulse of electrons to flow between the electrodes. Registers as a count on a meter. Energy:

Activity:

Decay Rate:

Mass Charge Typical Energy Range in air Penetration in matter Ionising ability

α Heavy +2 5MeV

β Light -1 1MeV

γ None None 0.1MeV

A few cm 10^-2 mm

1 or 2 m A few mm

Many m High

High

reasonable

Poor

Measurement of exposure:   ...