A World of Light and Color Activity 5

A World of Light and Color Activity 5

Shadows
Procedure and Results Sheet

Key Questions:

§  What are the different parts of a shadow?

§  Are shadows always black?

5.1

Materials:

§  Arbor Scientific light box and power supply

§  Large light bulb in reflecting holder

§  All the colored filters

§  Opaque filter-mask with no slits on one side and two on the other

§  Cylindrical object and color pencil (to act as an object in Part II)

§  Colored pencils for drawing

§  Meter stick

§  White sheet of paper and piece of cardboard with hole in it

§  White surface

Part I

Procedure:

1.  Look at the set-up below. When the light is on, there will be a shadow cast on the white surface. On your Predication Sheet, draw what you think the shadow pattern will look like.

2.  Now turn the light on. In the space below carefully draw the shadow pattern you see and discuss why it looks that way. Draw light rays on the figure below to help further develop your argument.

3.  Now turn the light off.

4.  On your Prediction Sheet draw what you think the shadow will look like when the lamp is 20 cm from the white surface.

5.  Turn the lamp back on and slide it into position, 20 cm from the white surface. In the space below carefully draw the shadow pattern you see and discuss why it looks that way. Draw your own picture, with light rays, to add to your explanation.

6.  Now turn the light off, again.

7.  On your Prediction Sheet draw what you think the shadow will look like when the lamp is as far from the white surface as you can move it.

8.  Turn the lamp on and slide it into position, as far from the white surface as possible. In the space below carefully draw the shadow pattern you see and discuss why it looks that way. Draw your own picture, with light rays, to add to your explanation.

9.  Turn the lamp off and move it so it is 50 cm from the white surface.

10.  Look at the set-up below. Notice that there is piece of cardboard, with a hole punched in it, between the lamp and the object. On your Predication Sheet, respond to the following questions and statements. When the light is on, will there be a shadow cast on the white surface? If so, then on your Predication Sheet, draw what you think the shadow pattern will look like. If not, explain why on your Prediction Sheet.

11.  Now place the cardboard between the lamp and object as indicate above, and turn the light on. In the space below, draw what you see on the white surface and discuss why it looks that way. Draw light rays on the figure below to help further develop your argument.

12.  Now turn the light off and replace the cardboard with a white sheet of paper, which doesn’t have any holes in it. (See below.)

13.  On your Predication Sheet, respond to the following questions and statements: When the light is on, will there be a shadow cast on the white surface? If so, then on your Predication Sheet, draw what you think the shadow pattern will look like. If not, explain why on your Prediction Sheet.

14.  Now turn the light on. In the space below carefully draw what you see on the white surface and discuss why it looks that way. Draw light rays on the figure below to help further develop your argument.

PART II

1.  Replace the cylindrical object with a colored pencil, balanced on the flat end. Place the pencil about 4 cm from the white surface. Also, replace the lamp with the light box, and move the front of the light box so it is about 20 cm from the white surface. Do not turn the light box on, but be sure both flaps on the box are open to an angle of about 45o with respect to the side of the box. (See below.) You will not need the white sheet of paper nor the cardboard for the following activities.

2.  On your Prediction Sheet draw what you think the shadow pattern on the white surface will look like when you turn the light box on.

3.  Now turn the light box on. In the space below carefully draw the shadow pattern you see and discuss why it looks that way. Construct a drawing with light rays to help support your drawing of the shadows.

4.  Do the shadows cast by the pencil have umbrae and penumbrae? Explain. Use a sketch of the set-up to aid with your explanation.

5.  On your Prediction Sheet draw what you think the shadow pattern on the white surface will look like after you close the flap on the left (when the light box is viewed from above). After that, on your Prediction Sheet, draw what you think the shadow pattern on the white surface will look like after you close the flap on the right (when the light box is viewed from above) while keeping the left flap closed.

6.  Now actually close the flap on the left and record what you see in the appropriate box below. Follow that by closing the other flap. Record what you see the appropriate box below.

7.  Discuss the important changes you witnessed as you closed the flaps.

8.  Turn off the light box and place the color filters in the holders as shown below.

9.  With the light box still off, close both flaps. Now, on your Prediction Sheet, make a prediction about the pattern of shadows and colors you will see on the white surface when you turn on the light box.

10.  Turn on the light box and record your observations below.

11.  Now turn off the light box and open the flap covering the blue filter so the flap makes an angle of about 45o with respect to the edge of the light box. On your Prediction Sheet, make a prediction about the pattern of shadows and colors you will see on the white surface when you turn on the light box.

12.  Turn on the light box and record your observations below.

13.  Now turn off the light box and open the flap covering the red filter so the flap makes an angle of about 45o with respect to the edge of the light box. (Both flaps are now open.) On your Prediction Sheet, make a prediction about the pattern of shadows and colors you will see on the white surface when you turn on the light box.

14.  Turn on the light box and record your observations below.

15.  Turn the light box off and slide the opaque filter-mask half-way down in front of the green filter. (Be sure you are sliding in the side of the filter-mask that has no slits in it.) On your Prediction Sheet, make a prediction about the pattern of shadows and colors you will see on the white surface when you turn on the light box.

16.  Turn on the light box (!) and record your observations below.

17.  Turn off the light box and replace the blue with the cyan filter, the red with the magenta filter, and the green with the yellow filter. On your Prediction Sheet, make a prediction about the pattern of shadows and colors you will see on the white surface when you turn on the light box and all the flaps are open.

18.  Turn on the light box (!) and record your observations below.

19.  Using all of the filters at your disposal, create cool shadow patterns. ; ) Record you favorite below.

PART III – Eclipses

1.  Imagine that you are located on the Earth at the position labeled A. If you were looking at the Sun from that position, how would it appear?

Never look directly at the sun under any circumstances. you will seriously damage your eyes. Results can include, but not be limited to, permanent blindness. (Hey, it happened to Galileo; it’ll happen to you.)

2.  If you were at B, what would the Sun look like? How about at C?

3.  Let’s say the Moon is just a bit closer to the Earth, as shown below, how would your above answers change?

4.  Now consider the arrangement below. If you were at positions A, B or C what would the Moon look like?

5.  What about this arrangement?

5.1