15 Radiation & Lasers

Refers to the waves or their photons (particles) from an electromagnetic field • Radio waves • Microwaves • Infrared light • Visible light • UV light • X rays • Gamma rays

Force field that consists both electric and magnetic components resulting from the motion an electric charge and containing a definite amount electromagnetic energy

Electrons flow around wire induce magnetic field around the wire Wire coiled repeatedly around an iron core

Expresses dual nature electricity and magnetism Electric current + magnetic waves Changing magnetic waves = electric current

Trough to trough Peak to peak

Number oscillations Shorter wavelength = higher frequency & stronger energy

Reflects directly back to source

Reflects indirectly

Reflects indirectly at lower frequency

Light not reflected

Energy emission Non-ionizing (visible, UV or infrared light, radio waves, microwaves) Ionizing (beta, gamma, or X-rays)

300mrem

Neutrons are excessive → convert to proton and electron Electron ejected at high speed Travels only few meters in air before being absorbed Shielding w/ radiation-absorbing material necessary

2 protons & 2 neutron are ejected as 1 particle Heavy & slow Travel only few cm in air before energy expended

Nucleus in excited state emits “energy packet” known as photon Number protons & neutrons are not altered but instead the nucleus moves from higher to lower energy state Travel long distances & shielding best achieved w/ lead

Less energy than gamma rays & less penetrating Require less shielding

Radiation w/ enough energy to remove tightly bound electrons from atom orbit Causes atom to become charged or ionized Alpha, beta, gamma, & X-rays (UV)

Absorbed dose - amount energy deposited per unit mass (grays Gy or milligray mGy) Equivalent dose - absorbed dose multiplied by converting factors based on biological radiation effects (sieverts Sv or millisieverts mSv) Amount ionizing radiation required to produce the same biological effect as one RAD high-penetration X-rays RAD radiation absorbed dose Milliroentgen mrem

Portable X-ray machine that are used in ORs & ICUs X-ray beam directed toward the patient and tube Stand at least 6ft away to minimize exposure

Distance from source Barriers (shielding) Exposure time

Distance from the source Intensity = 1/d^2 6ft away = 0.5mm lead shielding

Light Amplification Stimulated Emission Radiation Light emitted when electrons jump from more distant orbitals to orbitals closer to the nucleus

Monochromatic Coherent Collimated - light has minimal dispersion yielding narrow light band • Generate intense light beams • Send beams efficiently & accurately through lenses • Deliver intense energy to small target site

UV <400nm & visible wavelengths <500nm Photo absorption excites molecules & react to form unwanted chemical products cause erythema & vesiculation