light and matter

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Across
  1. 3. the matter from which a thing is or can be made
  2. 5. the colored ring within your eye
  3. 6. travels in a strait line
  4. 7. when you make a model to the exact size
  5. 9. the opening at the center of the iris through which light passes.
  6. 10. a material thing that can be seen and touched
  7. 12. To go through
  8. 15. an extension of your central nervous system, which includes your brain and spine.
  9. 17. the innermost light-sensitive membrane covering the back wall of the eyeball
  10. 18. a set of things working together as parts of a mechanism
  11. 21. any substance that has mass and takes up space by having volume
  12. 23. 50% of light goes trough
Down
  1. 1. Most light transmits through this material
  2. 2. a simplified drawing showing the structure of something
  3. 4. throwing back light without absorbing it
  4. 8. we use them to see
  5. 11. all light reflects off this material
  6. 13. to bounce off
  7. 14. a transparent double-convex lens.
  8. 16. a fact or situation that is observed to exist or happen
  9. 19. a communication system
  10. 20. serves as a barrier against dirt and particles
  11. 22. Type of energy that travels in straight line