QW 1-14 Draw a Venn Diagram to compare and contrast Transverse and Longitudinal Waves

Early Concepts of Light The Greek philosopher Socrates thought that vision resulted from streamers emitted from the eyes.

Christian Huygens Wave Model of Light Christian Huygens ( ), a Dutch mathematician and scientist, proposed a wave theory of light. The wave theory of light states that light travels in waves in all directions from its light source.

Isaac Newton's Theory of Color Isaac Newton , an English mathematician and scientist proposed that sunlight is a blend of all the colors of the rainbow. He demonstrated his theory by passing light through a prism of glass, which separated it into separate colors.

Electromagnetic Waves James Clerk Maxwell 1831–1879, a Scottish scientist, showed that light is a wave that is partly electric and partly magnetic. Such a wave is called an electromagnetic wave.

Electromagnetic Spectrum Light, radio, infrared, and ultraviolet are forms of energy that travel in waves called electromagnetic energy. Together these forms of energy form the electromagnetic spectrum.

Wavelength The distance from crest to crest is the wavelength. Each type of electromagnetic radiation has its own characteristic wavelength.

Frequency The frequency of a wave is the number of waves that pass a given point per second. Each type of electromagnetic radiation has its own characteristic frequency.

Frequency and Wavelength If light was a train, the wavelength would be the length of one car and the frequency would be the number of cars that pass each second. The frequency of train cars is the number of cars that pass per second.

Energy of Electromagnetic Radiation The shorter the wavelength, the higher the energy of the electromagnetic wave. An X ray has roughly a trillion times the energy of a radio wave. A photon (light particle) of gamma radiation has an energy of 1 million electron volts, while a photon (radio particle) of radio has the energy of only 1 millionth electron volt.

Radio waves have wavelengths that range from 1 to thousands of meters, while light has wavelengths of billionths of a meter.

Radio waves have frequencies of thousands of waves per second while light has frequencies of billions of waves per second.

For example, Denver’s Radio KOA 850 broadcasts at 850,000 waves per second. Its wavelength is 353 meters.

Radio Waves Radios Walkie-Talkies Television Signals

Microwaves –Shorter Wavelength than radio waves but much higher frequency –Cause fat and water molecules to move faster and get warmer Cell Phones

Infrared Radiation

Infrared Infra means “below” Heat Remote controls for electronics Security Devices

The Visible Spectrum The visible spectrum consists of wavelengths that are visible to the human eye. These are the colors of the rainbow, red through violet.

Colors: ROYGBV nm — wavelength of red light nm — wavelength of orange light nm — wavelength of yellow light nm — wavelength of green light nm — wavelength of blue light nm — wavelength of violet light

For example, red light has a frequency of 460 trillion waves per second and a wavelength of 650 billionth of a meter.

Red light consists of longer wavelengths and lower frequencies than violet light. Violet light consists of shorter wavelengths and higher frequencies than Red light.

Ultra Violet Tanning Salons Sun Burns Special UV lamps

X-Rays High Energy waves that pass through most substances

Gamma Rays Extremely high frequency waves. Difficult to control – Concrete or lead Used to treat some types of cancer