2. Light Can Act Like Waves or Particles In 1801 Thomas Young an English scientist did the Double slit experiment. In 1801 Thomas Young an English scientist did the Double slit experiment. Passed a beam of light through two narrow openings and projected it onto a screen. Passed a beam of light through two narrow openings and projected it onto a screen. He found the light produced a striped pattern which meant the light was constructively and destructively interfering. He found the light produced a striped pattern which meant the light was constructively and destructively interfering. This meant that light is composed of waves. This meant that light is composed of waves.

3. But Light can Also Behave like a Particle Other observations indicated that light can also act like a particle: Other observations indicated that light can also act like a particle: –When light hits metal it knocks electrons off the surface. –They found that red light cannot knock electrons off metal no matter how bright it is. –If light were a wave then the brighter light should have more energy. –Photons are light particles that contain certain amounts of energy based on their frequency and wavelength. –Blue light has a higher frequency and shorter wavelength thus contains more energy than red light.

4. Relationship Between Frequency, Wavelength and Energy

5. The Color of light is Determined By its Frequency and Wavelength Red 650 - 720 nm Red 650 - 720 nm Orange 570 - 650 nm Orange 570 - 650 nm Yellow530 - 570 nm Yellow530 - 570 nm Green 480 - 530 nm Green 480 - 530 nm Blue440 - 480 nm Blue440 - 480 nm Indigo410 - 440 nm Indigo410 - 440 nm Violet380 – 410 nm Violet380 – 410 nm

6. The Perception of Color Our perception of blending colors is created by how our eyes function. Our perception of blending colors is created by how our eyes function. –If a beam of red light and a beam of yellow light are shined together we do NOT perceive orange light. –Your eyes contain receptors called cones that are sensitive to red, green, and blue light. –These are known as the primary colors. If only the blue cones are stimulated then we will only perceive blue light. If only the blue cones are stimulated then we will only perceive blue light. –If more than one type of cone is stimulated then we will perceive a new color. –These are known as secondary colors. –If all three types of cones are stimulated we perceive white. –If none of the cones are stimulated we don’t see any color or perceive black.

7. The frequency and wavelength of light determine what color you will see. The frequency and wavelength of light determine what color you will see. –When you optical receptors perceive a wavelength of 550 nm you see green light. –The colors that you see are a result of surfaces reflecting various wavelengths of light back to your eyes. –White light When all of the primary colors are being reflected back to your eyes. When all of the primary colors are being reflected back to your eyes. –No light (or black) When all of the primary colors are being absorbed and no light is being reflected back to your eyes. When all of the primary colors are being absorbed and no light is being reflected back to your eyes.

8. The Brightness of Light Depends on Intensity Intensity Intensity –The quantity of light illuminating a surface. –Depends on the amount of light passing through a certain area or space. –Light spreads out in spherical wave fronts. –Light is more diffuse further from its source.

9. Primary Pigments Pigments are substances that absorb light. Pigments are substances that absorb light. The primary pigments are: The primary pigments are: –Cyan Magenta Yellow These are also known as the subtractive colors. These are also known as the subtractive colors. –Adding any of these two colors together give you back the primary colors.

10. ROYGBIV

11. Human Eye Cone Sensitivities

12. Color Addition

13. Reflected Red + Green = Yellow Reflected Blue + Green = Cyan Reflected Blue + Red = Magenta

14. Color Addition