Exploring Light: Absorb, Reflect, Transmit or Refract?

In designing laser-based security systems, engineers consider the implications of the penetrating properties of electromagnetic radiation. The concepts of wave absorption and transmission are fundamental in the design of laser based security systems, and have additional applications in biomedical engineering. In x-ray imaging, various tissue types result in a range of transmittances that can be recorded to depict bones on x-ray film. Engineers must also be aware of safety concerns; even low doses of high-energy radiation can be dangerous, especially in the case of gamma radiation. For cancer radiation treatments, control of high-energy radiation can be beneficial, but must be carefully managed. Students consider the potential real-world uses of various types of radiation in questions 2 and 5-9 of the post-activity assessment handout.

After this activity, students should be able to:

• Explain the properties of light as related to security systems.
• Describe which objects reflect, absorb or transmit light.
• Explain light refraction as applied to rainbows that appear in nature.
• Identify a number of applications of radiation to science and technology today.

This activity also meets the following Tennessee Foundations of Technology educational technology content standards: 2.0, 3.0, 4.0, 5.0, 6.0, 7.0 and 8.0.

This activity also meets the following National Science Education Standards (NSES) teaching standards: A, B, C, D, E, F; see https://www.nap.edu/topic/

A basic understanding of light properties as presented in lesson 2, Learning Light's Properties.

Today's activity brings a little fun and excitement to the concepts we have recently learned. The purpose of today's hands-on exploration is to reinforce your understanding of how different materials respond to a beam of light. We will explore light absorption, transmission, reflection and refraction. To explore refraction, you will create your own rainbow in the classroom. For the activity, you will spend 15 minutes at each of four stations set up throughout the classroom, answering questions and recording your predictions and observations on a worksheet.

With an understanding of the properties explored in this activity and an understanding of lasers gained in a future lesson and activity, you will be able to design your invisible laser security system to protect our mummified troll.

Background

This activity provides students with a hands-on means of exploring the light properties of reflection, absorption, transmission and refraction.

Before the Activity

• Gather materials and make copies of the attached Exploring Light Properties!Worksheet (PDF)and What have you learned today? Handout, (PDF)one each per student.
• Tip: Once you gather the materials to do this activity with your students, go through the activity first yourself. That way, you can fill in the results for the worksheet chart, based on the exact materials and light source (flash light) that your students will be using, essentially creating your own answer key.
• Set up the stations as described in the Materials List section. Set up station 1 in the darkest area of the room. Depending on class size, more than one station 1 may be helpful.
• Divide the class into groups of three students each for exploring each station; assign each group to a starting station.

With the Students

1. Hand out the worksheets.
2. For station 1: Direct student teams to follow the instructions on their worksheets and record both their predictions and observations.
3. For station 2-4: Direct student teams to fill out their worksheets by first predicting whether the light will be absorbed, transmitted or reflected, as well as the color of the resultant light. Then experiment to find the results and record their observations.
4. Lead a class discussion in which students share and compare their results and conclusions. See the Assessment section for a description of typical results.
5. To conclude, have students individually complete the handout.

Activity Embedded Assessment

Worksheet & Discussion: As students go through the stations, have them complete the worksheet chart with their predictions and results. In a class discussion, have students share and compare their results and conclusions. Results will vary, depending on the exact materials and light sources used, but in general, expect:

• reflective materials, such as aluminum foil and the mirror, to reflect the light
• solid, non-transparent materials, such as wax paper, body parts, notebook paper and cardboard paper, to absorb the light
• materials that have varying degrees of transparency, such as plastic saran wrap and tissue paper, to transmit the light
• the lighter colored tissue paper to most likely transmit more light than the darker colored tissue paper
• materials such as cheeks and notebook paper to transmit some light, although most likely absorbing most of the light

Post-Activity Assessment

Concluding Handout: After the activity, have students return to their desks and individually complete the What have you learned today? Handout (PDF). This assessment contains both content questions and application questions in which students consider applications to designing a security system.

Dictionary.com. Lexico Publishing Group, LLC. Accessed December 29, 2008. (Source of vocabulary definitions, with some adaptation)