December 12 Set up a New Notes Page for Ch 17 We are starting with 17.2 All Ch 17 Vocabulary Due Tomorrow Missing school this week? See Mrs. Bowen to get assignments before you leave
Chapter 17 Section 2 Electromagnetic Waves have many uses
Electromagnetic Waves have different wavelengths & frequencies Lower frequency Higher frequency The wavelength & frequency determine its characteristics
The Electromagnetic Spectrum shows the range of frequencies & wavelengths https://imagine.gsfc.nasa.gov/images/science/em_spectrum_compare_level1_lg.jpg
By Inductiveload, NASA - self-made, information by NASABased off of File:EM_Spectrum3-new.jpg by NASAThe butterfly icon is from the P icon set, P biology.svgthe humans are from the Pioneer plaque, Human.svgThe buildings are the Petronas towers and the Empire State Buildings, both from Skyscrapercompare.svg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=2974242
http://www2.lbl.gov/microworlds/alstool/emspec/emspec2.html
Radio & Microwaves Long Wavelength Low Frequency
Radio Waves Long wavelength & low frequency Travel easily through the atmosphere and many materials
Radio Waves Different radio stations broadcast different frequencies (the number you dial to is the frequency)
Radio Waves Radio transmitters attach information to the radio signal in two ways Modify the amplitude (AM radio) Modify the Frequency (FM radio) By Berserkerus - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=5071748
Broadcast television uses radio waves
Microwaves Long wavelength & low frequency Radar, cell phones, microwave ovens
Radar Transmits microwaves, receives reflections of the waves, converts the pattern into images on a screen Used in WWII for detecting aircraft & ships
Radar Air traffic control measure speed of vehicles study weather patterns By Fábio Pozzebom/ABr (Agência Brasil [1]) [CC BY 3.0 br (http://creativecommons.org/licenses/by/3.0/br/deed.en)], via Wikimedia Commons
Microwave Ovens Developed shortly after WWII How a microwave works (3 minutes) https://www.youtube.com/watch?v=xdm_gkpplck https://pixabay.com/en/microwave-oven-appliance-kitchen-29056/
Cell Phones Cell towers send and receive EM signals that are between FM radio & microwave
A large amount of evidence has failed to show a connection between cell phone radiation and cancer (read about this at the links below if you wish) https://www.cancer.org/cancer/cancer-causes/radiation-exposure/cellular-phones.html https://www.cancer.gov/about-cancer/causes-prevention/risk/radiation/cell-phonesfact-sheet Some would argue that we still need to be cautious as more information is gathered and as cell phone use increases
Infrared, Visible, Ultraviolet Medium Wavelength Mid range Frequency
Infrared Frequency Between microwaves and visible light Humans perceive infrared waves as warmth or heat radiating from something
Infrared Infrared scopes and cameras convert it into visible wavelengths so we can perceive the general pattern of infrared By NASA/IPAC [Public domain], via Wikimedia Commons
Vipers, pythons and boas have pit organs - holes on their faces that detect infrared radiation from warm bodies Photo credit: Julius Lab at UCSF
Ultraviolet Frequency above visible light but below x-rays Carries a lot of energy which can cause damage
Ultraviolet Can damage skin and eyes Can damage (or kill) bacteria used to sterilize
Some insects see patterns on flowers reflected by UV light humans cannot see
Scorpions glow under UV light https://www.flickr.com/photos/furryscalyman/297624007
X Rays & Gamma Rays Short Wavelength High Frequency
X-Rays Very high frequency and high energy Pass easily through soft tissue absorbed by dense tissue (bones and some tumors)
X-Rays Can be damaging and even cancer causing if exposed a lot Lead vests protect by blocking the radiation
Gamma Rays The highest frequency and energy of any EM wave Produced by radioactive substances in nuclear reactions Produced by the sun, & other stars
Gamma Rays Gamma radiation is sometimes carefully directed and used to treat cancerous tumors, especially in the brain
Gamma Rays Are blamed for making Bruce banner become the Incredible Hulk
Electromagnetic wave song https://www.youtube.com/watch?v=p_pvz8hrrci