Wave Stations – Waves at boundaries
Station #1
Station #2
Penny in a Cup
Procedure
1. Place an empty cup on the table and drop a penny in it. Look down into the cup so that you can see the
penny just over the lip.
2. Then, move back away from the cup slowly until the penny just disappears from your sight (below the lip).
3. Slowly pour water into the cup and the penny will come back into sight.
Questions
1. What type of wave behavior allows for
this visual trick?
2. Briefly explain why you were able to see
the penny only after you filled the cup
with water. (use the diagram for help)
Disappearing Stirring Stick
Procedure
1. Take the stirring stick and place it into the beaker which is filled with
“immersion” fluid (Wesson Oil).
2. From a side view look inside the beaker.
Describe what you observe.
Give your best explanation for what you see.
Questions
1. Which wave behavior relates to this activity?
2. On the diagram to the right, label the two areas where
refraction is occurring.
Station #3
Bending Lasers!
Before we begin:
1. What is more dense, water or air? ___________________________
Part 1: Air to water
Shine the laser from the air into the water. Measure the angle of the laser in the air and the angle of the laser
coming out in the water. The angles are always measured from the vertical line. Complete the chart below.
Angle in (air)
Angle out (water)
30 °
45 °
70 °
Part 2: Water to air
Now, start with the laser in the water. Measure the angle of the laser in the water and the angle of the laser
coming out of the air. The angles are always measured from the vertical line. Complete the chart below.
Angle in (water)
Angle out (air)
30 °
45 °
70 °
Part 3: Total internal reflection
Move the laser around slowly while pointed from the water toward the air until you are able to find the place
where the laser light does not make it out of the water (no light is seen in the air). This is called total internal
reflection.
What was the angle needed for total internal reflection? ____________________
Part 4: Conclusions
1. When light goes from a less dense material to a more dense material, what happens to the angle?
2. When light goes from a more dense material to a less dense material, what happens to the angle?
3. For total internal reflection to happen, do you have to go from a more dense to a less dense material, or
from a less dense to a more dense material?
Station #4
The Law of Reflection
1.
2.
3.
4.
5.
6.
First place your sheet on top of the wood board.
Set the mirror and the laser on your paper in the assigned spots (laser position 1)
Trace the beam coming in to the mirror and then trace the beam reflected from the mirror.
Put arrows on each beam for the direction it is going
Measure the angle in and the angle out with the protractor and label them on your diagram.
Repeat the process placing the laser at the second laser position
Conclusion about the law of reflection
1. What does the word reflect mean?
2. What was true about the angle coming in and the angle going out?
Station #5
Why are Sunsets Red?
DIRECTIONS: Place the light source so that the beam shines
through the container. Observe the light from the side AND
opposite end of the container. Note the color of the light. Repeat
for box B.
Questions:
1. What was the color of the light in box A?
2. How did the color of the light change when viewed from the side when you observed it in box B?
3. How did the color of the light change when viewed from the opposite end when you observed it in box B?
4. Read the paragraph below and put the information in picture/diagram form. Make sure your picture is
labeled.
5. The water in the experiment represents the Earth’s ________________ and the powdered milk represents
____________________________.
“Why Are Sunsets Red?”
At noon when the sun is directly overhead the sky appears blue. This is because the gas molecules in the
Earth’s atmosphere absorb and then emit (scatter) blue light in all directions, giving the sky a uniform blue
appearance. When the sun rises or sets it is lower on the horizon and has to travel through more of the Earth’s
atmosphere. This causes even more of the blue light to be scattered so that very little of it reaches our eyes.
The longer wavelength colors that are left, like pink, orange and red, are for the most part able to pass through
the atmosphere to our eyes with little to no change. This is why sunrises and sunsets are often pink, red and
orange in color. By the time the light reaches us, most of the other colors have been scattered away from our
view. When more of the sun’s light passes through a thicker layer of atmosphere, more reds continue on to be
seen by our eyes. The most spectacular sunrises and sunsets occur when there are more molecules in the
atmosphere than usual. More dust and smoke particles in the air from, say volcanoes or pollution, causes even
more scattering so that less pinks and yellows reach our eyes. When this happens, more oranges and reds reach
our eyes causing sunrises and sunsets that are even more intense or situations where the sun and sky can appear
red during the middle of the day.
Station #6
Why is your shirt blue?
**DO NOT point the laser at ANYBODY – if I see you doing this, you are done for the day.
1. Shine the red laser through the red gummy bear. What do you see?
2. Shine the green laser through the green gummy bear. What do you see?
3. Now, shine the red laser through the green gummy bear and the green laser through the red gummy bear.
How do these look different?
4. Shine the white like through both the green and the red gummy bears. How do they light up?
5. Click through the computer explanation of why we see color:
(http://apollo.lsc.vsc.edu/classes/met130/notes/chapter19/color.html)
Use this to explain the results from the gummy bears.
6. Now, shine the red and green lasers through the tip of your first finger. What happened?
7. Use everything you just learned to explain why they say to wear white in the summer.
Station #7
Specular vs. diffuse
1. Hold the shiny “daily bell schedule” 3-4 inches from the lightbulb. Try to read the words on the page.
2. Hold the non-shiny “receipt of …” the same distance away. Try to read the words.
3. Which one is easier to see? How do they reflect differently? Why do you think this is happening?
4. Read the article at your table and then answer the questions below:
5. What is specular reflection? Sketch a diagram.
6. What is diffuse reflection? Sketch a diagram.
7. Is the light bouncing off the magazine specular or diffuse? Why?
8. Is the light bouncing off the newspaper specular or diffuse? Why?
9. Is your shirt a specular or diffuse reflection of light? Why?
10. Can you think of some other examples of these 2 types of reflection?