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http://www.darvill.clara.net/emag/index.htm

Do Now• Take a clicker• Take a Do Now; put aside.• Take a POGIL – do the Warm Up#1-9

Homework:• As always, whatever you did not finish in class

becomes HW. (POGIL from today)• Read & Study corresponding sections in Ch. 27.• Do #11-17, 20-23 (12 points – 1 per #, 1 correctness)

Demo• Fill out the DO NOW portion of your chart

Overview of Radiation • Although scientists have only known about

radiation since the 1890s, they have developed a wide variety of uses for this natural force.

• Today, to benefit humankind, radiation is used in medicine, academics, and industry, as well as for generating electricity.

• In addition, radiation has useful applications in such areas as agriculture, archaeology (carbon dating), space exploration, law enforcement, geology (including mining), and many others.

• Nrc.gov

Radio Waves• Used for communication– Radios– Cell phones– TV – Some forms of wifi

• RADAR – Doppler effect from radio waves to image things

Microwave Radiation • Used for cooking • Also used for communication (similar to radio waves)• This is why some people say cell phones will give you

brain cancer• Common sense: don’t take unnecessary risks– Keep wifi routers in areas where they aren't constantly

next to people– Try not to sleep with your phone next to your head– Cell phones in pockets…? – Took decades for science to conclude that smoking was

bad for human health…. May or may not find something similar with all of the ‘wireless’ technology aka radiation

Infrared Radiation • Given off by all warm objects and produce heat in all

objects they strike. • The earth is warmed by infrared radiation from the sun.• Infrared lamps (incandescent lamps that emit mostly

infrared radiation) are used for:– drying paint, wallpaper, and printing ink; – keeping food warm in restaurant kitchens; – providing warmth in outdoor waiting areas during cold

weather; (Shake Shack)– for therapeutic heat treatments. – Remotes and lasers used to read CDs, DVDs, etc.

• Face detection in cameras – more on this later!

Infrared Radiation • Infrared radiation can be detected by various electronic

devices which make it possible to obtain images of the infrared radiation reflected or produced by an object: – check the heat insulation of a building/windows,– identify sources of thermal pollution in bodies of water, – in medicine to detect abnormally warm areas of the body,

revealing the location of diseased tissue.– In the military, as an aid in locating enemy troops at night,– and devices that detect infrared radiation emitted by aircraft

are used to guide certain antiaircraft missiles.– In night vision goggles – and in mapping the distribution of vegetation and other

resources on the earth's surface.

Visible Light Radiation • ROYGBIV• All we can see!

UV Radiation • Emitted by the sun and UV bulbs; • Responsible for triggering skin to produce melanin

and tan/burn; • Used to kill germs:– nail salons use them to sanitize equipment – they look

like toaster ovens that glow purple. – Also, the goggle cabinet in the back of this room uses UV

light• Used to detect counterfeit money, cards, and documents

More on this next class!

Examples of UV damage:

Examples of UV damage:

Examples of UV damage:

Skin CancerScars

UV cont.

A very bad case of skin cancer Localized skin cancer

X-Rays

X-Rays cont.• INJURY TO THE SKIN AND UNDERLYING TISSUES FROM

ACUTE EXPOSURE TO A LARGE EXTERNAL DOSE OF RADIATION IS REFERRED TO AS CUTANEOUS RADIATION INJURY (CRI).

X-Rays Cont.Full Term fetus (what is wrong with this picture?)

X-Rays were over used many years ago and people were gravely injured….See next slide.

X-Rays cont.Over exposure of the hand. This is an early x-ray technician’s hand. Over-exposed ankle

Gamma radiation• Gamma Radiation has the shortest wavelength and

the highest frequency in the EM spectrum.

Are wavelength and frequency directly or inversely proportional?

1. 2. 3.

0% 0%0%

1. Directly2. Inversely 3. Not sure

Gamma cont.• Best known for the Hollywood blockbuster,

“The Incredible Hulk”. This is of course, fiction!!!!!

Gamma Cont. Hiroshima and Nagasaki: The Atomic Bombings and Resultant Biological Effects of Radiation

Gamma cont.

Alpha, beta and gamma penetration Most extreme

POGIL - Check in at stop signs! Not going over whole thing as a class!

Stopping with 10 minutes left for a graded clicker exit

Generally speaking… is it safer to be exposed to high or low frequency radiation?

1. 2.

0%0%

1. High2. Low

Do high frequency EM waves have any benefits?

1. 2. 3.

0% 0%0%

1. Yes2. No 3. Not sure

Would you rather be exposed to Millimeter wave technology, or backscatter X ray technology, at the airport security checkpoints??

1. 2. 3.

0% 0%0%

1. Millimeter wave2. Backscatter X-Ray3. Not sure

Light that reflects at glancing angles from nonmetallic surfaces, such as glass, water, or roads, vibrates mainly in the plane of the reflecting surface.

27.7 Polarization

Light travels in waves. The fact that the waves are transverse—and not longitudinal—is demonstrated by the phenomenon of polarization.

• If you shake the end of a horizontal rope, a transverse wave travels along the rope.

• The vibrations are back and forth in one direction.• The wave is said to be polarized.

If the rope is shaken up and down, a vertically polarized wave is produced. The waves traveling along the rope are confined to a vertical plane. If the rope is shaken from side to side, a horizontally polarized wave is produced.

27.7 Polarization

A vibrating electron emits a polarized electromagnetic wave. • A vertically vibrating electron emits vertically polarized light.• A horizontally vibrating electron emits horizontally polarized light.

27.7 Polarization

An incandescent or fluorescent lamp, a candle flame, or the sun all emit light that is not polarized. The electrons that produce the light vibrate in random directions.

BUT –

When light shines on a polarizing filter, the light that is transmitted is polarized.

27.7 Polarization

A rope analogy illustrates the effect of crossed sheets of polarizing material.

27.7 Polarization

If POLARIZED light tries to pass through a filter…

Besides sunglasses… what other uses of polarizing filters can you think of?

27.8 Polarized Light and 3-D Viewing

A pair of photographs or movie frames, taken a short distance apart (about average eye spacing), can be seen in 3-D when the left eye sees only the left view and the right eye sees only the right view.

27.8 Polarized Light and 3-D Viewing

A 3-D slide show uses polarizing filters. The left eye sees only polarized light from the left projector; the right eye sees only polarized light from the right projector.Each eye sees a different image, and when the brain combines the images, you get a feeling of depth.

27.8 Polarized Light and 3-D Viewing

Does light travel in a transverse or longitudinal wave?

1. 2. 3.

0% 0%0%

1. Transverse2. Longitudinal 3. Not sure

Which pair of glasses is best suited for automobile drivers? (The polarization axes are shown by the straight lines.)

1. 2. 3. 4. 5. 6. 7.

0% 0% 0% 0%0%0%0%

1. A2. B3. C4. A & B5. B & C6. A B & C7. None of the

above

think!Which pair of glasses is best suited for automobile drivers? (The polarization axes are shown by the straight lines.)

Answer: Pair A is best suited because the vertical axes block horizontally polarized light that composes much of the glare from horizontal surfaces.

27.8 Polarized Light and 3-D Viewing

Which pair of glasses is best suited for 3D movies? (The polarization axes are shown by the straight lines.)

1. 2. 3. 4. 5. 6. 7.

0% 0% 0% 0%0%0%0%

1. A2. B3. C4. A & B5. B & C6. A B & C7. None of the

above

Exit Slip

• Please fill out the exit portion of your slip and turn in

• CLICKERS RETURNED IN ORDER!