Light and the Electromagnetic Spectrum

Waves… a review Most waves are either longitudinal or transverse. Sound waves are longitudinal. But all electromagnetic waves are transverse…

Light Phenomenon Isaac Newton (1642-1727) believed light consisted of particles By 1900 most scientists believed that light behaved as a wave.

Electromagnetic waves Produced by the movement of electrically charged particles Can travel in a “vacuum” (they do NOT need a medium Travel at the speed of light Also known as EM waves

The Electromagnetic Spectrum The electromagnetic spectrum represents the range of energy from low energy, low frequency radio waves with long wavelengths up to high energy, high frequency gamma waves with small wavelengths.

Frequency Ranges Wavelengths Frequencies (cycles per sec) 104 101 1 10-2 10-5 10-6 10-8 10-10 10-12 Frequencies (cycles per sec) 3 x 106 3 x 1010 3 x 1014 3 x 1016 3 x1018 3 x10 22

Radio waves Longest wavelength EM waves Uses: TV broadcasting AM and FM broadcast radio Avalanche beacons Heart rate monitors Cell phone communication Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens Bluetooth headsets Broadband Wireless Internet Radar GPS Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Infrared Radiation Wavelengths in between microwaves and visible light Uses: Night vision goggles Remote controls Heat-seeking missiles Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Visible light Only type of EM wave able to be detected by the human eye Violet is the highest frequency light Red light is the lowest frequency light Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

RedOrangeYellowGreenBlueIndigoViolet Visible light is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors. RedOrangeYellowGreenBlueIndigoViolet ROY G BIV

Ultraviolet Shorter wavelengths than visible light Uses: Black lights Sterilizing medical equipment Water disinfection Security images on money There is one more UV slide…

X-rays Tiny wavelength, high energy waves Uses: Medical imaging Airport security Inspecting industrial welds Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Gamma Rays Smallest wavelengths, highest energy EM waves Uses Food irradiation Cancer treatment Treating wood flooring Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram