For a deeper understanding of light, read the article, "light."
1. Write your predictions about how plants will grow under the different kinds of lights and other wavelengths. Give 2 pieces of evidence for your claim.
2. Examine the lights and read about the different kinds of wavelengths on the information cards before writing your predictions.
3. If time allows, draw and label the wave.
Note: Mrs. Lundy;s class did not plant seeds, but Mrs. Brown's class planted them for you all...
READING UP.... RESOURCES
Refraction and the Ray Model of Light - Lesson 1 - Refraction at a Boundary
The Cause of Refraction
We have learned that refraction occurs as light passes across the boundary between two media. Refraction is merely one of several possible boundary behaviors by which a light wave could behave when it encounters a new medium or an obstacle in its path. The transmission of light across a boundary between two media is accompanied by a change in both the speed and wavelength of the wave. The light wave not only changes directions at the boundary, it also speeds up or slows down and transforms into a wave with a larger or a shorter wavelength. The only time that a wave can be transmitted across a boundary, change its speed, and still not refract is when the light wave approaches the boundary in a direction that is perpendicular to it. As long as the light wave changes speed and approaches the boundary at an angle, refraction is observed.
The Marching SoldiersBut why does light refract? What is the cause of such behavior? And why is there this one exception to the refraction of light? An analogy of marching soldiers is often used to address this question. In fact, it is not uncommon that the analogy be illustrated in a Physics class with a student demonstration. A group of students forms a straight line (shoulder to shoulder) and connect themselves to their nearest neighbor using meter sticks. A strip of masking tape divides the room into two media. In one of the media (on one side of the tape), students walk at a normal pace. In the other media (or on the other side of the tape), students walk very slowly using baby steps. The group of students walk forward together in a straight line towards the diagonal strip of masking tape. The students maintain the line as they approach the masking tape. When an individual student reaches the tape, that student abruptly changes the pace of her/his walk. The group of students continues walking until all students in the line have entered into the second medium. The diagram below represents the line of students approaching the boundary (the masking tape) between the two media. On the diagram, an arrow is used to show the general direction of travel for the group of students in both media. Observe that the direction of the students changes at the "boundary."
The fundamental feature of the students' motion that leads to this change in direction is the change in speed. Upon reaching the masking tape, each individual student abruptly changes speed. Because the students approach the masking tape at an angle, each individual student reaches the tape at a different time. The student who reaches the tape first, slows down while the rest of the line of students marches ahead. This occurs for every student in the line of students. Once a student reaches the boundary, that student slows down while his/her nearest neighbor marches ahead at the original pace. The result is that the direction that the line of students is heading is altered at the boundary. The change in speed of the line of students causes a change in direction.
Conditions of RefractionWill this refractive behavior always occur? No! There are two conditions that are required in order to observe the change in direction of the path of the students:
The Marching Soldiers analogy provides an excellent analogy to understanding the cause of light refraction. The line of students approaching the masking tape are analogous to a wavefront of light. The masking tape is analogous to a boundary between two media. The change in speed that occurred for the line of students would also occur for a wave of light. And like the marching students, a light wave will not undergo refraction if it approaches the boundary in a direction that is perpendicular to it.
The same two conditions that are necessary for bending the path of the line of students are also necessary for bending the direction of a light ray. Light refracts at a boundary because of a change in speed. There is a distinct cause-effect relationship. The change in speed is the cause and the change in direction (refraction) is the effect.
spectrometer discussed below
1. What is refraction?
2. What is reflection?
3. Do humans see all forms of light?
1. With a partner, look through a prism and draw the direction the light goes.
a. Add a flashlight to the experiment and shine it through the prism. Where does the light go?
b. Draw what you see.
3. Finally, use mirrors and shine the flash light into the mirror and see if you can make the light go in different directions.
4. Once all students have investigated with prisms, flashlights, and mirrors, then come to the carpet and watch teh quick video, "light," then discuss refraction, reflection, and how much light people see.
How does light appear to other living things?
I can write about waves. Write a topic sentence and give
2 supporting facts for each question.
1. What are waves and how do they transfer energy?
2. Is a radio wave the same length as a visible light wave?
3. Describe the water and tuning fork experiemnt in the STEM Lab. What happened to the water when you put the tuning fork in. Use a topic sentence, and 3 supporting facts.
I can describe what I learned in the STEM Lab about the structure of a wave.
OPEN JOURNAL QUIZ:
Teachers, draw several waves on the board, and the vocaulary words.
1. Draw and label a wave. Use the words:
2. Which wave is longer, Visible light, or an X-ray?
3. Which wave is more powerful, Visible light, or an X-ray?
Review the electromagnetic spectrum with the NASA Youtube and the NASA photo (link) of the electromagnetic spectrum on this page.
WEEK 6 IN CLASS
I CAN DIAGRAM
PICK A WAVELENGTH AND
1. DRAW IT OUTSIDE WITH CHALK.
2. DRAW A COMPLETE WAVELENGTH CHART IN YOUR NOTEBOOK. INCLUDE THE DEVICES THAT USE EACH WAVELENGTH.