SHPE FoundationSHPE Jr. Chapter

CurriculumHands-on Activity Training

TeachEngineering Hands-on Activity:

*Light Intensity Lab

TeachEngineering Digital Library:

teachengineering.org

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TeachEngineering Digital Library

• The TeachEngineering digital library provides free, teacher-tested, standards-based engineering content for K-12 teachers to use in science and math classrooms.

• Engineering lessons connect real-world experiences with curricular content already taught in K-12 classrooms.

• Mapped to educational content standards, TeachEngineering's comprehensive curricula are hands-on, inexpensive, and relevant to children's daily lives.

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

http://www.teachengineering.org

General Advice• Be prepared! Do each activity beforehand

• Make sure all materials are available

• Keep students on task

• Follow the time frame

• Be flexible

• Have Fun!!

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

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Light Intensity Lab

• Light intensity, light attenuation• Engineering focus:

o Engineering Research/Analysis • Perform an experiment to observe the

relationship between light intensity and attenuation layers.

• Develop a rule (equation) based on empirical data that can be used in future applications.

• Learning objectives:o Derive the relationship between light intensity and

the number of layers of attenuation.o Perform experiments to illustrate the concept of

attenuation.

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Full Activity on TeachEngineering

http://www.nibib.nih.gov/science-education/science-topics/x-rays

Light Intensity Lab• Suggested time: 50 minutes

• Suggested group size: 3 students/group

• Materials (per group):• lamp• Incandescent 60W bulb (not halogen)• 12” x 12” piece of aluminum foil• clean transparencies• printed light intensity scale (print each one,

photocopies may not show the correct grayscale detail)

• 12” masking tape• scissors• Access to Excel or a graphing calculator• Light Experiment Handout (student version)

• For the instructor: • Light Experiment Handout (teacher version)

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

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Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Engineering Connection (Real World Application):

• Light attenuation and Beer's Law are engineering concepts that are very important for many engineers.

• Environmental engineers use this concept when building solar panels as a means of alternative energy.

• NASA has used the concept of attenuation (with radio waves) to determine information about Saturn’s rings.

• Biomedical engineers use these concepts in the design of x-ray machines, and also in other broader applications such as the field of biomaterials.

o In this activity, measuring bone mineral density using x-ray machines is used as the motivation engineering connection for the experiment.

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Vocabulary Terms

Definitions/Equations

Beer’s Law Beer’s Law relates how much light is absorbed by a material it is passing through to properties of that material. More specifically, Beer’s Law calculates the number of photons striking a detector (N) based on the number of incident photons (N0). For the case of an x-ray:

where μs and μb represent the mass attenuation coefficients (cm2/g) of soft tissue and bone (respectively) and Ms and Mb represent the area densities (g/cm2) of the two tissue types.

Light Attenuation The loss of light intensity as light passes through a material. The extent of attenuation is based on the light entering the material and properties of the material.

Light Intensity

where I = light intensity, I0 = light intensity when light does not pass through any medium, μ = attenuation coefficient (based on material light passes through and light energy), l = path length of the light

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Activity Procedure: Before the Activity:

o Make sure each group is able to work at a table pushed up against a wall to shine the lamp onto and take intensity measurements (limit the group numbers/ increase the group size if necessary).

o Experiments must be performed with the room lights turned off and the shades drawn – only using light from the lamps.

o Make copies of the worksheet for each group.

o Set out materials at each work station.

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Activity Procedure: With the Students:

o Tape the light intensity scale to the wall just above the surface of the table, and set up the lamp to shine on the scale (do not turn on the lamp yet).

o Cut the transparency into eight equal-sized pieces.

o Take a piece of foil and cut a 5 mm diameter hole in the center of it.

o Next, cover the face of the lamp by wrapping the aluminum foil around it, making sure that the hole is in the center of the face of the lamp and that the foil does not cover the vents in the back of the lamp.

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Activity Procedure (cont.): o Darken the room, turn on the lamp, and hold a piece of

transparency a couple inches from the wall to cast a shadow near the scale (but not on the scale).

o Match the intensity of the resulting shadow on the wall with a square on the scale. (Note: It’s easier to distinguish the matching shade of gray if you step back to look at it.)

o Record the intensity in Table 1 on the first page of the worksheet.

o Repeat the process with two sheets of transparency stacked together, then three, and so on until the table is filled.

o Use Excel to plot the natural logarithm of the shadow’s intensity versus the thickness of the attenuator. (Instructions provided on the worksheet – if computers are not available, have students use graphing calculators and graphing paper to create this graph.)

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Thickness = Number of Transparencies

Light Intensity

Natural Log of Intensity = ln(intensity)

0 100 4.605170186

1 96 4.564348191

2 90 4.49980967

3 88 4.477336814

4 84 4.430816799

5 81 4.394449155

6 78 4.356708827

7 77 4.343805422

Ln(Intensity) vs. Thickness

y = -0.0385x + 4.5937

R2 = 0.9834

4.3

4.35

4.4

4.45

4.5

4.55

4.6

4.65

0 2 4 6 8

Thickness (# of sheets)

Ln

(In

ten

sity

)

Sample Results

Light Intensity Lab

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Teaching tips: o Emphasize the science concepts, vocabulary, and engineering

connection; reinforce these throughout the activity.

o Ask students if they have ever had an X-ray. Explain that the concepts explored in this activity are what allowed engineers to develop X-ray technology! Ask them if they think they would have healed from injuries as well if doctors were not able to use X-rays.

o Once students have made their graphs, discuss the results as a class. Ask students if they discovered a relationship between the layers of attenuation (layers of transparencies) and the light intensity. Ask them what this suggests about light (or x-rays) passing through dense materials versus less dense materials.

o Have fun and encourage students to have fun!!

Activity Takeaways• Teambuilding skills

o Making decisions, sharing tasks and materials

• Engineering skillso Engineering Analysis: performing an experiment, taking

quantitative measurements, analyzing results, relating results to real world problems and technologies.

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

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• Encouragement through life experienceso Relate this activity to the experience of

having an x-ray. Emphasize how students are discovering the concepts involved in designing an X-ray machine.

• Motivation through having funo Introduce the activity as a fun learning

experience!

TeachEngineering Contact

Information• TeachEngineering: http://www.teachengineering.org/

o over 1,200 standards-based engineering lessons and activities

• Carleigh Samson, TeachEngineering Editoro carleigh.samson@colorado.eduo 303.492.6950

SHPE Foundation

SHPE Jr. Chapter Curriculum

Hands-On Activity Training

Questions?

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