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 f

requency

. • 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 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,

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.

Radio

Exploring the EMS with

Infrared

NASA Missions

Visible UV X-ray Gamma ray MAP SWAS ASTRO-E2 Swift GALEX Chandra RXTE CHIPS HETE-2 Con-X INTEGRAL XMM-Newton GLAST Energy (eV)

And the universe for that matter!