- Discuss and review how the behavior

1. TODAY’S OUTCOMES: BEHAVIOR OF LIGHT - Discuss and review how the behavior of shadows is related to the size and distance of the object from the light source - Understand how ray diagrams are used to determine the behavior of shadows - Investigate how reflection from a flat surface works.

2. Explain how to use your graph to infer where you would need to place the cylinder in order to make a shadow that is 10 cm wide. Find the point on the horizontal axis (representing distance) that corresponds to 10 cm on the vertical axis (representing shadow size). Why did the instructions say to observe the width of the shadow and not the height? The shadow “blur” along the width of the shadow can be minimized by narrowing the filament of the bulb in the direction of the projected light. The shadow on the top and bottom of the object always has some “blur”, because the filament width cannot be adjusted along the vertical direction.

3. Louise has a great idea how to decorate her living room for when she hosts the bridge club next week: she will draw hearts and spades on the light bulbs, so that they project these pictures onto the lampshade and the ceiling. Easy to do, cheap, and after the party she can just wash the pattern off. Her neighbor Margie objects, "If that’s going to work, why doesn't it say '100 Watts' on the ceiling already?" Is Margie right, that this won't work? Or can you tell Louise how to rescue the scheme? Margie is correct - an object too close to a wide light source (in this case, the filament), will not project a sharp shadow. Louise could help this scheme by making a shade with “shapes” further from the light bulb, to make sharper shadows on the wall.

4. Drawing ray diagrams bright fuzzy dark fuzzy bright light source object surface You could draw this - but why do we draw it this way?

5. bright dark bright Consider a simple case - a tiny, “point” light light source object surface No “fuzzy” areas - each spot either gets light or it doesn’t

6. Let’s add a 2nd tiny light nearby light source object surface

7. Let’s add a 2nd tiny light nearby light source object surface

8. bright fuzzy dark fuzzy bright Let’s add a 2nd tiny light nearby light source object surface

9. Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface

10. 2 Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface How many lights would the fly see here?

11. 1 Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface How many lights would the fly see here?

12. 0 Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface How many lights would the fly see here?

13. 1 Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface How many lights would the fly see here?

14. 2 Let’s say you’re a fly...... bright fuzzy dark fuzzy bright light source object surface How many lights would the fly see here?

15. Back to the large light..... Imagine it as a bunch of tiny “point lights” - we’ll just look at the edges... light source object surface

16. Back to the large light..... Imagine it as a bunch of tiny “point lights” - we’ll just look at the edges... light source object surface

17. Back to the large light..... Imagine it as a bunch of tiny “point lights” - we’ll just look at the edges... light source object surface

18. The whole light source Back to the large light..... Let’s get the fly and ask what it sees.... light source object surface

19. Part of the light source Back to the large light..... Let’s get the fly and ask what it sees.... light source object surface

20. Back to the large light..... Let’s get the fly and ask what it sees.... light source object surface None of the light source

21. Part of the light source Back to the large light..... Let’s get the fly and ask what it sees.... light source object surface

22. All of the light source Back to the large light..... Let’s get the fly and ask what it sees.... light source object surface

23. It becomes like a point source again - the shadow becomessharp again. What if the light is REALLY far away?? light source object surface

24. All this applies to any source & surface source object surface

25. light dark light fuzzy fuzzy All this applies to any source & surface source object surface

26. - Shadows grow larger when they are closer to the source - Shadows from point-like lights cast very sharp shadows - Shadows from large light sources have a region of “fuzziness” that can be determined from ray diagrams WHAT YOU ARE EXPECTED TO KNOW:

27. TODAY’S OUTCOMES: BEHAVIOR OF LIGHT - Discuss and review how the behavior of shadows is related to the size and distance of the object from the light source✓ - Understand how ray diagrams are used to determine the behavior of shadows✓ - Investigate how reflection from a flat surface works.