Spots, Lines and Lasers

Students will experiment with lasers and cloth to test wavelength.

Students will collect and interpret their data to define what the wavelength of a laser is.

Draw what you think a light wave looks like.

Use a ruler to measure the distance between the crests (top of wave) in your drawing.

Do you think the space between the waves (wavelength) of a REAL light wave is more than the distance in your model, less than the distance in your model, or the same?

What tool do you think you could use to measure the real distance?

Draw what you think a light wave looks like.

Use a ruler to measure the distance between the crests (top of wave) in your drawing.

Do you think the space between the waves (wavelength) of a REAL light wave is more than the distance in your model, less than the distance in your model, or the same?

What tool do you think you could use to measure the real distance?

1. Pair students up
2. Give them a minute to think quietly
3. Give students 2 minutes to discuss their thinking
4. Have students record their answers or share out to the whole group

Optional: Look at the pieces of cloth under the microscope, magnifying glass, or just hold up to the light. Draw the patterns you see in your notebook.

Predict: What type of pattern do you think you will see when you shine the laser through a piece of cloth?

Tell students that the experiment they are about to do will help them explore these properties of light waves coming out of a laser, called wavelengths.

Assemble the Diffraction Grating Card as instructed on the card.

Attach binder clips so that the card can stand unsupported.

Place the card several meters from the wall. Measure this distance.

Tape a piece of paper to the wall so that the pattern created by shining the laser through the cloth falls on the sheet of paper.

Make sure students are put into intentional groups.

Students will complete the experiment using the Student Guide where we have outlined the experiment for students and along the way, they record results and answer questions.

Have students predict what patterns they think they will see when the laser shines through the different pieces of cloth.

(Optional) Have students look at the different swatches of cloth through the microscope and draw the patterns that they see into their notebooks. If you don’t have access to microscopes, try magnifying glasses, or just have students hold the swatches up to a light.

In the student guide, they will begin calculating the wavelength of a laser.

Continue to listen in on each group’s discussion, answer as few questions as possible. Even if a group is off a little, they will have a chance to work out these stuck points later.

Suggested STEP UP Everyday Actions to incorporate into activity

• When pairing students, try to have male/female partners and invite female students to share their ideas first
• As you put students into groups, consider having female or minority students take the leadership role.
• Take note of female participation. If they seem to be taking direction and following along, elevate their voice by asking them a question about their experiment.

Consider using white boards so students have time to work through their ideas and brainstorms before saying them out loud.

As students experiment, roam around the room to listen in on discussion and notice experiment techniques. If needed, stop the class and call over to a certain group that has hit on an important concept.

Consider using the RIP protocol (Research, Instruct, Plan) for lab group visits and conferring.

Consider culturally responsive tools and strategies and/or open ended reflection questions to help push student thinking, evidence tracking, and connections to their lives. Look for *** below to find suggested places to add

Discussion Diamond protocol

1. Setup: Each small group or table needs a copy of a graphic organizer that looks like the image to the right. Each student will write one of the triangular “corners” of the organizer.
2. The small groups should have one person from each experiment group, that way each student is coming in with different (but possibly similar) data.
3. Pose the question “What is the wavelength of a laser?”
4. All students get three minutes to think and write their thoughts in their respective corners.
5. The students take turns explaining their ideas to each other (all students must share).
6. The students discuss what their consensus view might be and write their consensus view in the middle.

After students have had a chance to discuss key ideas from the lesson and complete their student guides, you can now clarify and give concise definitions to the forces they experimented with.