Types of Radiation in the Electromagnetic Spectrum

1. Types of Radiation in the Electromagnetic Spectrum

2. We live in a sea of radiation… • Personal Radiation Dose • IONIZING AND NON-IONIZING RADIATION • Non-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

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

5. Ionizing radiation: X-Rays and Gamma • Strips an electron from a molecule • Molecule becomes positively charged. • Can cause the formation of free radicals

6. Free Radicals • Contain an unpaired valence-shell electron and are extremely reactive. • Destroy biologically active molecules • Either remove electrons or removing hydrogen atoms from them. • Damage the membrane, nucleus, chromosomes, or mitochondria of the cell; • this inhibits cell division • results in cell death • produces a malignant cell.

7. Ionizing particles—alpha & beta particles • Alpha • Nuclei of Helium • Charge = +2 • Stopped by a piece of paper • Beta • Beta- (electron emission) • Beta + (positron emission or electron capture) • Positron • They cause most damage when they are emitted inside the human body.

8. Gamma rays • Less ionizing • Damage includes burns and cancer through mutations

9. More about Ionizing Radiation • Dangerous in direct exposure (degree of danger is a subject of debate) • Animals (including humans) can also be exposed to ionizing radiation internally • if 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.

10. Ionizing Radiation Principal Effect of low doses: to induce cancers which don’t manifest for 20 years Principal Effect of high doses: • More immediate effects • Cells 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.

11. Non-ionizing radiation • 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.

12. Effect of 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.

13. Fatal Doses • Non-Ionizing: 7 moles of photons of visible light • Ionizing: • 300 joules of x-ray or gamma-ray radiation lethal • Even 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!

14. Uses • Kill cancerous cells • Generate electricity • Problem: waste produces ionizing radiation • Radiography—enhancing images that are hard to capture, such as inside the body. • Irradiating food • Medical sterilization • Sterile insect technique