Radiation Friend or Foe? - ILLINOIS PHYSICS...Cell phone frequency bands About 109 Hz (1 GHz)...

RadiationFriend or Foe?

Saturday Physics for Everyone7‐Oct‐2017Kevin Pitts

7‐Oct‐2017 Saturday Physics Kevin Pitts ([email protected]) 2link

Thank you Toni for 14 years of Saturday Physics, and your service to our students.

Outline• What is radiation?

– Discuss different types– Where we encounter radiation

• How does radiation affect us?– The good and the bad

7‐Oct‐2017 Saturday Physics Kevin Pitts ([email protected]) 3

Question• Would you eat food that has been irradiated?• What’s scary about radiation?


Radiation• Definition: the emission of energy as electromagnetic waves or as moving subatomic particles, especially high‐energy particles that cause ionization.



• Radiation carries energy– Energy example: slow/fast car, slow/fast bus



• Different types: EM or subatomic particles



• High‐energy radiation causes ionization




Start with electromagnetic waves.

Electromagnetic Spectrum


Faraday cage and radio

Infrared “heat” radiation

• The Predator could see Arnold in the infrared


IR camera

Infrared radiation• Objects radiate in the infrared• It’s a way to cool off!• Any ideas about what else cools itself by emitting IR radiation?




Non-ionizing. Energy too low to break atomic bonds

microwave

Can cell phones cause brain cancer?


Cell phone frequency bands About 109 Hz (1 GHz)



Non-ionizing. Energy too low to break atomic bonds

microwave

Ionizing!

Ionizing radiation• Can break chemical bonds• Can break DNA strands

– Mutations!

• Can be:– bad (cancer, birth defects) or – good (cancer treatment, polymer creation)

• Fortunately, for DNA we have autocorrect.


DNA double helix

X‐rays• Penetrate very deeply (great for imaging!)

• Ionizing – enough energy to break bonds• Radiation dose from 1 x‐ray tiny


Ultraviolet radiation is ionizing• UV exposure (not visible or IR) can cause skin cancer.


More radiation, more cancers• Linear effect: bigger dose, cancer more likely• Measured (mostly) from atomic bombs


Sv = Sievert100 rem=1 Sv

Typical person (per year): 300mrem=0.3rem=0.003Sv


• Radiation carries energy– Energy example: slow/fast car, slow/fast bus

• Different types: EM or subatomic particles• High‐energy radiation causes ionization


Radioactivity• When atoms (nuclei) produce radiation.


Alpha decay


Geiger counter

Alpha particle is really a helium nucleus. Helium safe (balloons! squeaky voices!) so why is alpha radiation potentially dangerous?

Beta radiation

Example: 14C → 14N +


TV+magnet

Beta particle is really an electron. Electrons safe (electricity!) so why is beta radiation potentially dangerous?

7-Oct-2017 Saturday Physics Kevin Pitts ([email protected]) 25

Radiation from space• Earth’s atmosphere and magnetic field protect us from cosmic radiation.

Cloud chamberLink link


National Research Council

“At the present time, given current knowledge, the level of radiation astronauts would encounter would not allow a human crew to undertake a Mars mission and might also seriously limit long‐term Moon activity.”

International Space Station astronauts receive a radiation dose that is 27 times higher than we receive on Earth’s surface.The ISS is still protected by Earth’s magnetic field and upper atmosphere.


Radiation• Radiation would be sufficient to kill humans in long duration

space flight, unless an acceptable shielding method was developed.

• Perhaps other beings might be less susceptible to radiation effects.

Sources/Defenses• Many sources of radiation

– Natural: radon, cosmic rays, rocks– Artificial: X‐rays, nuclear medicine, consumer products

• Earth constantly bombarded by cosmic rays which produce both primary and secondary radiation.– Atmosphere (plus Earth’s magnetic field) provide excellent radiation shield.

– What if you have less atmosphere to shield you?• You get more radiation…airplane employees, astronauts…

• Our skin is also a good radiation shield.– Alpha and most beta particles stopped by skin, only do damage if ingested.


Estimate your annual dose.

Radiation therapy• Take advantage of cancer cells dividing quickly. • Small particle accelerator produces narrow beam of x‐rays.


Proton therapy• Less common, more complicated & expensive• But can be effective for deep tissue cancer


A bigger accelerator


Other radiation applications• Accelerator‐based radiation used for:

– Computer chips (iphone, PC)– Car tires– Diapers– Shrink wrap (meat packaging)– Furniture finish

• Other ideas under development– Safe nuclear reactors (ADS)– Stronger concrete


All safe!No residual radioactivity.

More than 30,000 accelerators in use worldwide, producing radiation for applications.

Conclusion• Radiation is both friend and foe

• Different types of radiation exist– Some are inherently safe (non‐ionizing)– Some can be unsafe, although still often helpful

• Lots of things to be concerned about, radiation should not be high on your list.


Radiation Friend or Foe? - ILLINOIS PHYSICS...Cell phone frequency bands About 109 Hz (1 GHz)...

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