General Lab Report Instructions The speed of light and radio wave propagation

Warm-up Two balls have the same displacement and travel for the same length of time. – Which ball traveled a greater distance? –Which ball traveled at a greater speed? –How far did the ball on the right travel? –How fast did the balls travel if they took 5 seconds? Wall 1m Displacement

Standards Physics 1a. Students know how to solve problems that involve constant speed and average speed. Physics 4e. Students know radio waves, light, and X- rays are different wavelength bands in the spectrum of electromagnetic waves whose speed in a vacuum is approximately 3x10 8 m/s. Investigation and Experimentation a. Select and use appropriate tools and technology (such as computer- linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

Objectives By the end of this assignment you should be able to: Describe the motion of radio waves as they propagate through the ionosphere. Calculate the speed of light using the constant velocity equation for displacement Design a model and an experimental method Collect, display and analyze data Write a conclusion and an abstract summarizing the results from a lab

Lab Positions Materials Manager –Collects and returns materials, writes lab introduction and abstract Recorder –Designs method, records and graphs data Leader –Analyzes data and draws a conclusion about the data Peer Reviewer –Reviews the quality of work of another group –Reports back to his or her strengths an weaknesses in the other group’s lab work. Determine Positions

Title and Abstract Title –shortest possible description of the lab –Not written in a complete sentence Abstract –concise description of the hypothesis, method and conclusion of the lab. –Short –Written after the very end of the lab –Displayed at the beginning of the report

Constants & Variables Constants are numbers and quantities that should remain fixed throughout the execution of the lab Variables are the quantities that will change –Independent variable can be changed –Dependent variable changes as a result

Relationships & Equations Relationships describe how changes in the independent variable effect changes in the dependent variable –Basic relationships Direct: increase in X  increase in Y Inverse: increase in X  decrease in Y Equations are often used to describe relationship patterns in data

Diagram Visual model of the lab Major parts are shown Parts are labeled with words or symbols –A key is given for symbols Force of Friction (F f ) Normal Force (N) Weight (mg) Component directions (  &  )

Introduction Testable experimental hypothesis is stated –Preliminary model is presented Relevant scientific knowledge is presented to help reader understand the hypothesis –Scientific laws and theories –Description of the constants and variables Assumptions are accounted for

Activity: Background Part I Read and Discuss background articles –Are there pictures that can aid in drawing the diagram? –What are the important concepts, theories, and laws that can be used to write the introduction? –Are any relationships or equations expressed? –What are the independent and dependent variables? Peer Reviewer: After reading, determine which group you will review and sit in on their discussion.

Activity : Background Part II Review the grading check list Begin drafting page one –You may want to do draft work on a separate sheet of paper Peer Reviewer –Rejoin your group –Report insights from the other group

Method The process of the lab Written in chronological steps Describes the tools and techniques used to change and measure variables Describes actions to control the activity Provides enough information for another group to repeat the lab

Activity: Method Read the experiment details handout Review the grading check list Develop the experimental method –How is the independent variable changed and measured? –How is the dependent variable measured? –How will the lab be controlled? –Is there enough information for another group to repeat the lab? –What calculations must be preformed? Peer Reviewer: Review and grade the same group from the previous activity.

End of Day 1 Homework –Materials manager: fill out page one –Recorder: write the method

Data Table Use columns to record measured data and intermediate calculations Show column headings with units Use significant figures to show limitations of the measurement tools Unexpected behavior should be noted Copy data for the independent and dependent variables in the two rightmost columns Data Table Independent Variable Dependent Variable

Activity: Data Collection Look over the data from the table in the handout –Are there any additional calculations required to find how far the signal traveled? –Hint: what geometric shape do you think represents the radio wave’s propagation path? –Show a sample calculation on the backside of the page In this lab the independent variable is the distance the signal traveled while dependent variable is the time the signal takes to travel that distance. Travel times are shown below. Record measurements in the data table. Fill in the independent and dependent variable column in the data table

Graphing: Scatter Plot Shows the data as points on a graph Full range of values evenly distributed on on each axis – Independent variable on X-axis –Dependent variable on Y-axis

Graphing: Best-fit Line Make an oval around the data Draw a line through data that divides the oval into equal areas Also called –Linear regression –Trend line ?

Graphing: Outlier Data Outlier data points do not fall into the general grouping of data Excluding outliers from analysis must be justified in the conclusion with specific evidence

Graphing: Slope A linear relationship shows a proportional change in the dependent variable for each change in the independent variable The proportional change is the slope y = mx + b slope(m)

Graphing: Slope Select two points on the line –(x 1, y 1 ) and (x 2, y 2 ) –NOT DATA POINTS

Activity : Graphing Create a scatter plot Draw a best-fit line Calculate the slope Circle any excluded outliers

Lab Questions Your teacher may assign questions that guide you in forming a conclusion.

Analysis: Percent Error Percent Error: measures how far off an experimental measurement is off from an accepted value A measure of experimental accuracy High Accuracy, Low Precision Photo: Wikimedia Commons

Analysis: Percent Difference Percent Difference: measures how far an experimental measurement is off from an average value Shows how far the data is spread out A measure of experimental precision High Precision, Low Accuracy Photo: Wikimedia Commons

Conclusion Describes and gives reasons for patterns in the data Explains how the pattern confirms or refutes the prediction, hypothesis or model. Explains differences in experimental, accepted values and class average values Identifies and gives reasons for the outlier data. Indicate problems with the method and discuses how they can be resolved.

Activity: Conclusion Read the grading check list Lab Questions –How does a radio wave interact with the ground and ionosphere? –What was the shape of the radio waves path? Calculate the percent error and percent difference Write the conclusion and abstract for the first page

Activity: Peer Reviewer Grade the other groups lab –Use the grading checklist –Record grades at the bottom of each page –Reviewer’s grade depends on how well their evaluation matches the teachers evaluation

Activity: Peer Reviewer Finish the lab activity by facilitating a fishbowl discussion with the peer reviewers –How did your group’s method, data and conclusion compare to those use by the group you review? –What were the challenges of the lab? –What were the challenges of the report? –How were differences between group members resolved? –Was the work evenly shared? How to conduct a fishbowl discussion

End of Day two Homework –Leader: Answer the questions, complete the data analysis, and write the conclusion. –Peer Reviewer: During the next class meeting you will read over and provide feedback on another group’s lab report.

Help Full Links Vision Learning: Scientific WritingScientific Writing Science Education Resource Center Carleton College: Graphing Overview Statistics Canada: Scatter Plots and RelationshipsGraphing OverviewScatter Plots and Relationships