Post on 27-Mar-2015
What Wavelength Was That?Examining the Electromagnetic Spectrum
with Hands-On Activities
Electromagnetic Spectrum
• The full range of frequencies, from radio waves to gamma rays, that characterizes light
• The electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way.
• The wavelength equals the speed of light divided by the frequency or lambda = c / nu
Electromagnetic Radiation
• Electromagnetic radiation can be described in terms of a stream of photons, each traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy.
• The only difference between radio waves, visible light, and gamma-rays is the energy of the photons. Radio waves have photons with low energies, microwaves have a little more energy than radio waves, infrared has still more, then visible, ultraviolet, X-rays, and gamma-rays.
Scaling the Spectrum Activity
• Helps to explain the electromagnetic spectrum and dispels some of the common misconceptions.
• Paper and pencil project that requires the use of math skills as well.
Wavelength and Frequency
• For any kind of wave there exists a simple relationship between wavelength and frequency.
• The wavelength is measured as the distance between two successive crests in a wave. The frequency is the number of wave crests that pass a a given point in space each second.
Understanding Waves
• The traditional “slinky lab” as well as other activities to help understand waves.
• An activity that allows students to experiment with waves-longitudinal and transverse.
• Found in “Waves Light Up the Universe” Booklet
Radio(Low Frequency & Very High Frequency)
• Emitted by– Astronomical Objects– Radio Station
transmitters
• Detected by– Ground based radio
telescopes– Radios
Umbrella Receiver Demo
• Students discover a method of collecting radio frequencies by using an umbrella receiver.
Microwave
• Emitted by:– Gas clouds collapsing
into stars– Microwave Ovens– Radar Stations– Cell Phones
• Detected by– Microwave Telescopes– Food (heated)– Cell phones– Radar systems)
Infrared(Near and Thermal)
• Emitted by– Sun and stars (Near)– TV Remote Controls– Food Warming Lights
(Thermal)– Everything at room
temp or above
• Detected by– Infrared Cameras– TVs, VCRs,– Your skin
Herschel’s Experiment
• Herschel’s Experiment– Discovered Invisible
Light– In 1800, Herschel
places his control thermometer just outside the red end of the spectrum
– Result: The outside thermometer registered the highest temperature
Conducting Herschel’s Experiment
• Set up of Box Design for Conducting the Herschel Experiment.
Conducting Hershel’s Experiment• Place a sheet of white paper
inside a cardboard box• Tape three thermometers
together and place inside box
• Cut a small notch in the top of the box and position a glass prism so that the spectrum is projected inside the box
• Arrange the thermometers so that one is just outside the red end of the spectrum, with no visible light falling on it
Visible
• Emitted by– The sun and other
astronomical objects– Laser pointers– Light bulbs
• Detected by– Cameras (film or
digital)– Human eyes– Plants (red light)– Telescopes
Roy G. Biv Activity
• Students will discover and verify the relationship between the Wavelength and Frequency of the EMS.
• Students compare the wavelength and frequencies of three colors of the visible light portion on the spectrum.
Red Sky – Blue Sky
• A demonstration used to illustrate how the gases in the atmosphere scatter some wavelengths of visible light more than others.
Ultraviolet
• Emitted by– Tanning booths (A)– The sun (A)– Black light bulbs (B)– UV lamps
• Detected by– Space based UV
detectors– UV Cameras– Flying insects (flies)
X-ray
• Emitted by– Astronomical objects – X-ray machines– CAT scan machines– Older televisions– Radioactive minerals– Airport luggage scanners
• Detected by– Space based X-ray
detectors– X-ray film– CCD detectors
Chandra X-ray Observatory
• Chandra is designed to observe X-rays from high energy regions of the universe, such as the remnants of exploded stars.
• The most sophisticated observatory built to date.
• Deployed by the Space Shuttle Columbia on July 23, 1999,
Chandra X-ray Observatory
Gamma Ray
• Emitted by– Radioactive materials– Exploding nuclear
weapons– Gamma-ray bursts– Solar flares
• Detected by– Gamma detectors and
astronomical satellites– Medical imaging detectors
Sources of g-ray Emission• Black holes• Active Galaxies• Pulsars• Diffuse emission• Supernovae• Gamma-ray bursts• Unidentified
Source/Detector Activity
• Students identify sources (emitters) and detectors of the various wavelengths of the EMS.
• Students also have the opportunity to experiment with shields –or types of materials that prevent the transmission of wavelengths.
Exploring the EMS withNASA Missions
ASTRO-E2
Chandra
CHIPS Con-X
GALEXGLAST
HETE-2
INTEGRAL
MAP
RXTE
SWAS
XMM-Newton
Swift
Energy (eV)
Radio Infrared Visible UV X-ray Gamma ray
And the universe for that matter!