Summary
Students revisit the mathematics required to find bone mineral density, to which they were introduced in lesson 2 of this unit. They learn the equation to find intensity, Beer's law, and how to use it. Then they complete a sheet of practice problems that use the equation.Engineering Connection
Students see the real-world connection with this material right away. Beer's law and the other equations that they learn in this lesson are mathematical tools that biomedical engineers use every day when they make bone mineral density readings. Environmental engineers also use light intensity measurements when designing solar panels and other forms of energy storage. Almost every type of engineer knows and uses Beer's law.
Learning Objectives
After this lesson, student should be able to:
- Apply their knowledge of logarithms to solve Beer's law problems.
- Explain the breath of the applications of logarithms.
More Curriculum Like This
Students examine an image produced by a cabinet x-ray system to determine if it is a quality bone mineral density image. Students learn about what bone mineral density is, how a BMD image can be obtained, and how it is related to the x-ray field.
Students examine the definition, history and relationship to exponents; they rewrite exponents as logarithms and vice versa, evaluating expressions, solving for a missing piece. Students then study the properties of logarithms (multiplication/addition, division/subtraction, exponents).
Students complete this Beer's law activity in class by examining the attenuation of various thicknesses of transparencies. From this activity, they come to understand that different substances absorb light differently.
Students continue an examination of logarithms in the Research and Revise stage by studying two types of logarithms—common logarithms and natural logarithm. They take notes about the two special types of logarithms, why they are useful, and how to convert to these forms by using the change of base f...
Educational Standards
Each TeachEngineering lesson or activity is correlated to one or more K-12 science,
technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN),
a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics;
within type by subtype, then by grade, etc.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
Common Core State Standards - Math
- Interpret expressions that represent a quantity in terms of its context (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Interpret parts of an expression, such as terms, factors, and coefficients. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Solve simple rational and radical equations in one variable, and give examples showing how extraneous solutions may arise. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Solve linear equations and inequalities in one variable, including equations with coefficients represented by letters. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Choose and produce an equivalent form of an expression to reveal and explain properties of the quantity represented by the expression. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- (+) Understand the inverse relationship between exponents and logarithms and use this relationship to solve problems involving logarithms and exponents. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- For exponential models, express as a logarithm the solution to ab^{ct} = d where a, c, and d are numbers and the base b is 2, 10, or e; evaluate the logarithm using technology. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Use the properties of exponents to transform expressions for exponential functions. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
- Rearrange formulas to highlight a quantity of interest, using the same reasoning as in solving equations. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
International Technology and Engineering Educators Association - Technology
- Technology transfer occurs when a new user applies an existing innovation developed for one purpose in a different function. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
Tennessee - Math
- (+) Understand the inverse relationship between exponents and logarithms and use this relationship to solve problems involving logarithms and exponents. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment?
Introduction/Motivation
Recall from lesson 1 that you are working for a company that makes small specimen cabinet x-ray machines for medical research. Today you will learn how to do some calculations with the data that you might collect from such a machine.
Lesson Background and Concepts for Teachers
Calculation of Bone Mineral Density:
The basic equations for dual-photon absorptiometry can be derived from a number of underlying assumptions. First, it is assumed that the material is composed of varying amounts of only two substances (in this case bone and soft tissue). Second, it is assumed that scatter can be ignored. Under these circumstances, for any given photon energy, the number of photons striking the detector (N) can be calculated from the number of incident photons (N_{o}) using Beer's law.
Beer's law:
where μ_{s} and μ_{b }represent the mass attenuation coefficients (cm^{2}/g) of soft tissue and bone (respectively) and M_{s} and M_{b} represent the area densities (g/cm^{2}) of the two tissue types.
I = I _{o} e ^{-μl}
I = Intensity.
I_{0} = Intensity with no object.
μ = attenuation coefficient (depends upon material and x-ray energy).
l = length of the x-ray path.
Lecture Information
Present to students the BMD Math Presentation, a PowerPoint® file. Then have students complete the BMD Math Practice Problems. Administer the Log Quiz 2. Then students are ready to conduct the associated activity, Light Intensity Lab.
To answer the Challenge Question introduced in lesson 1, students next must Go Public. Refer to the Pamphlet Poster Paper Instructions for how students are to present all that they have learned about logarithms and bone mineral density during the course of the entire unit.
Associated Activities
- Light Intensity Lab - In this lab exercise, students learn how to measure light intensity through transparencies.
Attachments
Assessment
Post-Introduction Assessment
Practice Problems: At lesson end or as homework, assign students to complete the BMD Math Practice Problems. Review their answers to assess the depth of their understanding.
Lesson Summary Assessment
Quiz: At lesson end, administer the 13-question, multiple-choice Log Quiz 2, which covers all types of logarithmic problems covered in this unit. Review students' answers to gauge their comprehension.
Student Presentations: In order to answer the unit challenge question first posed in lesson 1, have students create posters, pamphlest or papers, as described in the Pamphlet Poster Paper Instructions.
Contributors
Kristyn Shaffer; Megan JohnstonCopyright
© 2013 by Regents of the University of Colorado; original © 2006 Vanderbilt UniversitySupporting Program
VU Bioengineering RET Program, School of Engineering, Vanderbilt UniversityAcknowledgements
The contents of this digital library curriculum were developed under National Science Foundation RET grant nos. 0338092 and 0742871. However, these contents do not necessarily represent the policies of the NSF, and you should not assume endorsement by the federal government.
Last modified: July 20, 2017
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