Electromagnetic spectrum and visible light

1. Electromagnetic spectrum and visible light • What is each color made of? • Which color carries the most energy? How do you know?

2. How your eye sees color • Photons hit the retina • The retina contains two types of cells: rods and cones. • Rods process vision in low light - black, white, and shades of grey • Cones process color vision and detail • When photons collide with these cells chemical reactions occur and an electrical signal is sent along the optic nerve to the brain. • The retina contains 100 million rods and 7 million cones.

3. Emitted color – photons of different color are made and released Refracted Color – color is made when white light travels through a different medium and refracts Reflected Color – color made from photons that reflect from objects Ideas???

4. Emitted color • Photons with different energies will appear different colors • Emitted photons made from: • Chemical reactions • Stars • Red – lower temperature/less energy/ longer wavelength • Blue – higher temperature/more energy/ shorter wavelength Binary stars in Cygnus: Albireo A & B (380ly)

5. Fireworks – which color has the most energy?

6. Fire – a chemical reaction • Which color would have the shorter wavelength? • Which color would carry the most energy? • Zone 2 - bluish zone where carbon gas, C2, is released. This zone actually extends up around the outside of the flame but the blue color is usually only visible at the bottom the hottest part of the flame, reaching a temperature of around 1400°C • Zone 4:bright yellow area where carbon is being oxidized and burned, creating carbon dioxide (CO2) and carbon monoxide (CO). This zone has a temperature of about 1200°C with the bright yellow color coming from incandescent soot (carbon) particles.

7. Refracted Color • Which color has the highest frequency? How does white light turn into colored light?

8. Refracted Color • Red is slower (lower frequency) with less energy so red refracts or bends at a smaller angle (bends less) • Purple or Violet is faster (higher frequency) with more energy so purple refracts or bends at a larger angle (bends more)

9. Rainbows: reflection & refraction http://eo.ucar.edu/rainbows/

10. Reflected Color or Why is your shirt red? • All white light is made of the following colors (ROYGBV) • Red • Orange • Yellow • Green • Blue • Violet (purple) • white light (visible) lands on an object • some photons are absorbed by the object • some of the photons are reflected by the object. • reflected photons are what we see; the energy color of the photons. • objects are different colors; because they reflect some colors but absorb other colors. http://www.physicsclassroom.com/class/light/u12l2c.cfm (quiz)

11. Why is it that color?