- Discuss and review how the behavior of shadows is related to the size and distance of the object from the light source - Derive a law for the behavior of light in specular reflection - Learn how colors mix to create white light TODAY’S OUTCOMES: BEHAVIOR OF LIGHT

This diagram represents a small frosted light bulb, a mask with a large hole in it, and a screen. Light is emitted from all parts of the light bulb. Draw some straight lines representing the paths that light can take. Determine the region on the screen that will be completely dark, the region that will be lit by all parts of the light bulb, and the region that is neither completely dark nor completely lit.

bright fuzzy dark

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

All this applies to any source & surface source object surface

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

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. Louise has an 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 the '100 Watts' written on the light bulb show on the ceiling already?" Is Margie right, that this won't work? Or can you tell Louise how to rescue the scheme?

- 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:

- Discuss and review how the behavior of shadows is related to the size and distance of the object from the light source ✓ - Derive a law for the behavior of light in specular reflection - Learn how colors mix to create white light TODAY’S OUTCOMES: BEHAVIOR OF LIGHT