Wavelength is the Key What we see is much less than what we get. Opensource Handbook of Nanoscience and NanotechnologyOpensource Handbook of Nanoscience and Nanotechnology. Illustration by Kristian MolhaveKristian Molhave
Waves Transfer energy without transferring matter
Electromagnetic Energy Determined by wavelength and frequency. E = mc 2 c = 2.9979 x 10 8 m/s
Dual Nature of Light Light is also photons (particles) Zero mass and zero rest energy Can be destroyed and created Can have particle-like interactions with matter
Electricity and Magnetism Magnetism and electricity move together in the EM spectrum. Diagram from Schneider, Remote Sensing and the Global Environment, http://www.geo.mtu.edu/rs/back/spectrum /
Appearances May Deceive Optical properties vary at the nanoscale. Image source: L. R. Hirsch, R. J.Stafford, J. A. Bankson, S. R. Sershen, B. Rivera, R. E. Price, J. D. Hazle, N. J. Halas, & J. L. West, Proc. Natl. Acad. Sci. USA, 100, 13549- 13554 (2003). Proc. Natl. Acad. Sci. USA
Blocking Signals Activities Materials Needed Cell phone or small radio Small box with lid Aluminum foil Aluminum screen Scissors Tape and/or stapler ruler
Activity – Control Experiment 1. Turn on radio and set in box. 2. Place lid on box. 3. Turn off radio. 4. One (or more) group test with cell phone if available.
Activity – Box the Signal Wrap box and lid separately in aluminum foil (ensure snug fit). Set radio in box. Open box slightly (experiment with opening size). One (or more) group test with cell phone if available.
Activity – Screen the Signal Make a cylinder with aluminum screen. Leave one end open. Make a prediction. Place radio inside. Close other end of cage. Test with a cell phone if available.
Wavelength and Frequency Activity Wavelength c/f C = 3.0 x 10 8 m/s Example 300,000,000m/s) / (540,000 Hz) = 55.6 m Frequencies AM radio: 540-1640 KHz FM radio: 88-174 MHz Cell: 850-1900 MHz
What Size Mesh Do You Need? Mesh size 1/10 the wavelength
Activity: Building a Faraday Cage Remove foil from top of box lid. Cut several ½” strips of foil. Make a grid of strips on the lid. Experiment with size openings until a phone will not ring in box.
Data Analysis and Conclusions When using aluminum strips, what size openings worked to stop the radio? A cell phone? Why does the opening size matter in a Faraday Cage? What other materials could be used?
Wavelength Matters Locations where wireless equipment does not work Protection from electronic spies Space weather effects EMP