Physics Color Lab

To be completed in your lab notebook

Pre Lab:

  • On a fresh piece of paper in your lab notebook write today’s date and the title of the lab.
  • Don’t forget to continue the page numbers in your lab notebook.
  • Don’t forget to add this lab and its page number to your Table of Contents.
  1. How are shadows produced?
  2. Define “Color Addition.”
  3. Define “Color Subtraction.”

Copy the following key for colors that you will be using into your lab notebook:

R=RedB=Blue

G=GreenM=Magenta

C=CyanY=Yellow

W=WhiteK=Black

Your light box as viewed from above

Mixing Light

  1. Use the mirrored end of the ray box to mix primary red, primary green, and primary blue light on a white screen in all possible combinations. For best results, place the blue slide in the slot closest to the screen. Adjust the mirrors until you can produce white light on your screen.
  2. Glue in your “Light” diagram like at right:
  3. Then complete the light color chart below by doing the following:
  4. Write the letter of the color produced in the blank spaces.
  5. Color in the lettered red, green and blue portions of the circles with colored pencils or markers (preferably “Mr. Sketch” pens).

Do not color in the overlapping portions in this step.

  1. Now color in the overlapping mixture potions of the circles with appropriate colored pencils or markers (preferably “Mr. Sketch” pens).

Note: Red and green pigment do not produce the same color when mixed as red and green light. Therefore you are not asked to actually mix pigments on the light chart, but rather to use the pigments to represent light.

Mixing Pigments

  1. Glue in your “Light” diagram like at right:
  2. Use the colored pencils or markers (preferably “Mr. Sketch” pens) to complete the pigment color chart below.
  3. Using the yellow pen first, color each complete circle with the appropriate pen, allowing the pigments overlap.
  4. Then label each of the overlapping regions with the letter of the color produced.

Shadows

  1. Using the red, green, and blue filters (with the blue filter in the center) in all possible combinations, create as many different colored shadows as you can on the white screen by blocking light.
  2. Use an object such as a pencil or your finger to block the light, and try placing the blocking object at different distance from the screen.
  3. Make observations as you experiment about how different colored shadows are produced. You will need this information later to answer Analyzing Questions #1-8.

Interaction of Light and Pigment

  1. Remove the three filters and close the mirrored sides so that you have only one white light source.
  2. Use the red filter to project light on a white piece of paper.
  3. Use the red filter to project light on a red colored square.
  4. Use the red filter to project light on a green or blue colored square.
  5. Use the blue filter to project light on a green or redcolored square.
  6. Use the green filter to project light on a blue or redcolored square.

Chromatic Aberration

  1. Remove all filters from the mirrored side of your light box. Turn your light box around so that you use the other side of it with a lens on it.
  2. Put a 4-slit mask on this end of the light box and be sure that the four lines come out parallel. If they do not, call your teacher over.
  3. Use your thick convex lens (called the “cat eye” lens) to focus the white light from your ray box.
  4. Put a piece of paper underneath the lens and lightly mark the focal point.
  5. Carefully and without moving your equipment, add a blue filter to this side of the light box so that the parallel light rays coming out are blue.
  6. Carefully mark this blue focal point.
  7. Carefully and without moving your equipment, remove the blue filter and add a red filter to this side of the light box so that the parallel light rays coming out are red.
  8. Carefully mark this red focal point.

Analyzng:

Underneath your Pre-Lab questions, write “Analyzing” and you will answer the questions below in complete sentences. Don’t forget to number your answers!

4. How many different colored shadows can you produce?

5. List all the different colored shadows produced:

6. How is a red shadow produced?Be specific!

7. How is a yellow shadow produced?Be specific!

8. How is a black shadow produced?Be specific!

9. What color does the white piece of paper appear to be under red light? Briefly explain why it appears to be this color.

10. What color does the red piece of paper appear to be under red light? Briefly explain why it appears to be this color.

11. When observing the red filter on a green or blue colored square or the blue filter on a green or

red square or the green filter on the blue or red square, what color did you see? Note that due to dye

imperfections this may be difficult to see. Briefly explain why it appears to be this color.

12. The ______light is focused closer to the lens.