Thursday, April 18 Reminders: Yesterday's (Wednesday) assignment: Completed the lenses lab activity we started on Tuesday and answered the Ch. 30 Lenses questions wksht. Be sure you've turned these two assignments in before you leave today. Other reminders: Big test next week (Wed or Thur) covering Chapters 25-31 Portfolios will be due the day of the test.

New seating chart! Quietly gather all your items and stand around the periphery of the tables. Remain quiet as the new seating arrangement is called out. Be quiet and respectful as you move to your new seat so that the people still listening and watching for their name can hear/see. If problems arise (disruptions, etc.), then you will be moved to a different seat.

Video Warm-Up & Recap: color

Review: Color The color spectrum and prisms Color by reflection vs. color by mixture of colored light vs. color by transmission Variations of color due to the type of light source Absorption of light Scattering of light Today's video warm-up does a great job of summing up these concepts from Ch. 28 Color.

Chapter 28: Color Questions Pass back and review Assigned 4-8-13 5 points possible 1. Draw and label a prism as a beam of white light passes through it and is diffracted/dispersed into the different colors/frequencies of the light spectrum.

2. Are black and white real colors in the sense that red and green are 2. Are black and white real colors in the sense that red and green are? Explain. No. Black is not a color, but rather the absence of color (as it absorbs all visible colors/frequencies). White is not a color but a combination of all visible colors/frequencies. Under white light, white objects appear white and colored objects appear in their individual colors. 3. Explain why the color of an object will look different under a fluorescent lamp compared to when seen under an incandescent lamp. The perceived color of an object is subject to the light source, although color differences are most easily detected in bright sunlight. Incandescent bulbs enhance the lower frequencies (yellows), and fluorescent bulbs enhance the higher frequencies (blues).

4. What is the function of a pigment and how does it interact with color at an atomic level? Electrons in the pigment selectively absorb and reflect different light at only certain frequencies in the illuminating light. 5. Why are fire engines being painted yellow green instead of red? It is the brightest and easiest to see to the human eye; our eyes are most-sensitive to this frequency of color.

6. Do tiny particles in the air scatter high or low frequencies of light? High frequencies are scattered (the frequencies are absorbed and reemitted in all directions). 7. In terms of light frequencies and light scattering, explain why the sky is blue. Small molecules in the air (hydrogen, oxygen, etc.) scatter the high-frequency light (blue) hence coloring . 8. In terms of light frequencies and light scattering, explain why clouds are white. The mixture of different water droplet sizes scatters many frequencies of light.

What color is the sun?

9. In terms of light frequencies and light scattering, explain why the sunsets are red. Only low frequencies (reddish) of light are not scattered and filtered out on the long path through the atmosphere, leaving the lower red frequencies. 10. In terms of light frequencies and light scattering, explain why the ocean is greenish blue. Water absorbs reddish frequencies of light, leaving the higher blue and green frequencies to scatter in the water.

Concept recap : lenses and diffraction

Notice that lenses and mirrors act almost oppositely when comparing the behavior/path s of light in terms of reflection and refraction.

Today's assignment: 4-18-13 Ch. 29 Concept Practice worksheet Use straight edge to draw accurate ray paths on your ray diagrams. Remember, you must be careful and accurate, especially when drawing the angle of reflection equal to the angle of refraction.