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Reflection and Refraction Lab

Reflection and Refraction Lab 

 

Purpose:   The purpose of this lab is to learn about the behavior of light when it encounters a boundary separating two different materials.  


Intro

  • Definition:  Refraction refers to the change in direction of light that occurs when light goes from one material (like air) into a second material (like water).



  • Definition:  Reflection refers to the change in direction that occurs when light bounces off a material.  
  • Setup for the lab


  • The normal line is a line drawn perpendicular to the boundary between your two substances.

  • The angle of incidence is the angle the incoming light makes with the normal line.

  • The angle of reflection is the angle the reflected light makes with the normal line

  • The angle of refraction is the angle the refracted ray makes with the normal line.

Part 1:  Live Refraction from Air to Water

  • Place your polar graph paper on the cardboard and then put your semi-circular fish tank on the graph paper so that the vertical line on the tank lines up with the origin and so that the flat wall lies along the x-axis of the paper.



  • Imagine a normal line that is perpendicular to the flat side of the tank.

  • Place a pin 30° away from the normal line.  



  • Sight through the curved side of the tank and line up your 30° pin with the vertical marker line on the tank.  



  • Then place a second pin on the curved side of the tank so that both pins and the vertical line on the tank all appear to be in a single line.  Make sure you are looking through the water.



  • Record the location of the pins in a data table that lists incident angle and refracted angle and the change in angle.  Make enough rows for 8 different incident angles.

  • Repeat for a wide variety of incident angles.  For the largest angles you might need to place your pin closer to the tank.  Just stay on the proper angle line.

  • Q1:  Which angle is bigger, the incident or the refracted?

  • Q2:  What happens to the ∆angle as your incident angle gets larger?


Part 2:  Simulated Light Moving from Air to Water

  • In order to complete this part of the lab you are going to be using the program that can be found here

  • Your data table for this lab will contain three columns.  The first will be the incident angle, the second will be the reflected angle and the third will be the refracted angle.  

  • With your top material as air and the bottom material as water, collect data for at least 10 different angles.  If any of your rays are not visible, just put does not exist in the data table.

  • Open LoggerPro and put your angle of incidence on the x-axis.  Go to the Data Menu and select "New Manual Column" and put in your data for Angle of Reflection and Angle of Refraction in your data table.

  • Make a graph in Logger Pro that has both refracted and reflected angles on the y-axis and the angle of incidence on the x-axis.  The best way to get both columns to show up on your y-axis is the click on the title of the y-axis on your graph and select "All of the Above".   You do not need to curve fit your data.



  • Make conclusions about your angle of refraction and angle of reflection based on what you saw in part two of your lab.

Part 3:  Simulated Light Moving from Water to Air

  • Your data table for this lab will contain three columns.  The first will be the incident angle, the second will be the reflected angle and the third will be the refracted angle.  

  • Click on the link at the bottom of the program that allows you to switch the location of your light source so that the light moves from the water into the air.  So you should still have your top material as air and the bottom material as water, collect data for at least ten different incident angles with angles ranging from 0 to 90°.  If any of your rays are not visible, just put does not exist in the data table.  Remember, the refracted angle is the one that goes from Water into Air and the reflected angle is the one that stays in the water.  

  • Make a graph in Logger Pro that has both refracted and reflected angles on the y-axis and the angle of incidence on the x-axis.  You do not need to curve fit your data.

  • Make conclusions about your angle of refraction and angle of reflection based on what you saw in part one of your lab.


Part 4:  Changing the substance

  • Switch the position of your light source so that the light starts in the air and then passes into water.   Pause your program when the incident angle gets close to 60°, notice the amount of bending that takes place.

  • Make a data table that records the name of the substance you are passing into and the angle of the light when entering that substance.  

  • Click on the word water to change to a different substance.  Don't resume your program but just record the new angle of the refracted light.

  • Do this for all available materials.

  • Rank your materials based on the amount of bending that takes place.  Start with the material that bends the least and finish with the one that bends the most.

  • When you are done all four parts, answer the questions found here.

What you need in your lab book:

  • Purpose

  • A picture of the lab setup

  • The definitions from the information section of the lab.

  • All the data tables constructed neatly

  • A graph of angle of refraction vs. angle of incidence with all the things a good graph should contain.

  • A few sentences of conclusion and error analysis.
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