Types of Radiation in the Electromagnetic Spectrum

Personal Radiation DoseIONIZING AND NON-IONIZING RADIATIONNon-ionizing:

Carries LESS energy Can only excite the water molecule.

Ionizing:Carries MORE energy than 1216 kJ/mol Can remove an electron from a water molecule

We live in a sea of radiation…

Ionizing & non-ionizing radiation is a part of the electromagnetic spectrum

Strips an electron from a moleculeMolecule becomes positively charged.Can cause the formation of free radicals

Ionizing radiation: X-Rays and Gamma

Contain an unpaired valence-shell electron and are extremely reactive.

Destroy biologically active moleculesEither remove electrons or removing hydrogen

atoms from them.Damage the membrane, nucleus,

chromosomes, or mitochondria of the cell; this inhibits cell divisionresults in cell deathproduces a malignant cell.

Free Radicals

Ionizing particles—alpha & beta particlesAlpha

Nuclei of HeliumCharge = +2Stopped by a piece of paper

BetaBeta- (electron emission)Beta + (positron emission or electron capture)Positron

They cause most damage when they are emitted inside the human body.

Less ionizingDamage includes burns and cancer through

mutations

Gamma rays

Dangerous in direct exposure (degree of danger is a subject of debate)

Animals (including humans) can also be exposed to ionizing radiation internallyif radioactive isotopes are present in the

environment, they may be taken into the body. Example:

radioactive iodine is treated as normal iodine by the body and used by the thyroid

its accumulation there often leads to thyroid cancer.

More about Ionizing Radiation

Ionizing RadiationPrincipal Effect of low doses: to

induce cancers which don’t manifest for 20 years

Principal Effect of high doses: More immediate effectsCells that are actively dividing are

more susceptible to radiation exposure

Bone marrow & skin more likely to sustain injury than the central nervous system or the kidneys.

Has enough energy to make the atoms in a molecule vibrate, but not remove electrons

Large ranges:UV, visible light, infrared,

microwaves, radio waves, and other low frequency waves.

Thought to be essentially harmless below the frequencies that cause heating.

Non-ionizing radiation

At low-energy end of the electromagnetic spectrum: (radio waves and microwaves)Excites the movement of atoms and molecules, which is

equivalent to heating the sample. In or near the visible portion of the spectrum:

Excites electrons into higher-energy orbitals. When the electron eventually falls back to a lower-

energy state, excess energy is given off to neighboring molecules in the form of heat.

Principal effect of non-ionizing radiation = increase in the temperature of the system.

Effect of Non-Ionizing Radiation

Non-Ionizing: 7 moles of photons of visible lightIonizing:

300 joules of x-ray or gamma-ray radiation lethalEven though it only raises the temperature of the

body 0.001°C!Internally, alpha particle radiation is even more

dangerous; a dose equivalent to only 15 joules is fatal for the average human; 7 x 10-10 moles of the particles emitted by alpha

particles of 238U is fatal.Polonium-210 (alpha emitter) suspected in lung,

bladder cancer related to tobacco smoking!

Fatal Doses

Kill cancerous cellsGenerate electricity

Problem: waste produces ionizing radiationRadiography—enhancing images that are

hard to capture, such as inside the body.Irradiating foodMedical sterilizationSterile insect technique

Uses