Images, Images, Images

Materials: Computer, School Network, Protractor and Ruler

Time Allotment: 3 Class Days

Purpose:

The purpose of this lab is to investigate the nature of and the formation of the images created by plane mirrors and right angle mirrors.

Getting Ready:

  1. Log on to the server in the usual manner.
  2. Open the HyperCard application found in the Multimedia folder.
  3. From the File menu, choose Open... . A directory dialogue box will open. Navigate to the Physics Stacks and open the file titled Images, Images, Images. You will use the printout of a HyperCard stack to conduct your lab investigation.
  4. Click anywhere on the title card of the stack and you will navigate to the first part of the lab - Images in Plane Mirrors. A miniature snapshot of the appropriate card is shown below.

Part 1: Formation of Images by Plane Mirrors

When we look at an object in a mirror (or through a lens) we are looking at an image of the object. When an object is illuminated with light (or when it merely gives off light), light rays from the object are moving in a variety of directions. Some of these light rays from the object ultimately strike the mirror. These light rays reflect off the mirror, following the law of reflection. Some of them reflect towards the eye of an obsever, recreating the image on the back of our retina, which in turn our brain perceives and interprets. The image of the object in the mirror is the result of reflected rays. The actual image location is the location where reflected rays from the mirror intersect. This location can be either behind the mirror (if reflected rays diverge) or in front of the mirror (if reflected rays converge) But regardless of which side of the mirror the image is formed on, the image location is formed where the reflected rays intersect. To identify the image location, reflected rays must be traced forward or backwards until they intersect.

  1. Click anywhere on the right side of the mirror to locate an object. (If you can't tell left from right, then the computer will help you; just click somewhere.)
  2. Once you click at a point, the program locates an object at this point and draws several rays of light from this point to the mirror. Print this card by clicking on the Print Diagram button. You will no longer need the computer for Part 2. You may complete the first two steps of Part 2 and then return to these directions to use the printed diagram to complete Part 1.
  3. For each of the nine incident rays heading from object to the mirror, sketch a normal and use the law of reflection, a protractor and a straight edge to draw the appropriate reflected rays. Be as accurate as possible. Place arrows on all your rays to indicate their direction.
  4. Once you have drawn all nine reflected rays, use dashed lines to trace each of the reflected rays backwards until they intersect.
  5. Identify the image location by labeling it on the diagram and then answer the following questions.
    1. Measure the object distance and the image distance using a ruler. How do they compare?

       

    2. Locate an eye on the right side of the mirror by drawing a dot. Do not place the eye on one of the reflected rays. Label the eye (as "eye). Draw the incident and reflected light rays which would travel to the eye from the object in order for the person to see its image.

 

Part 2: Formation of Images by Right Angle Mirrors

  1. Click anywhere on the bottom-right side of the monitor to locate an object in between a right angle mirror.
  2. Once you click at a point, the program locates an object at this point and draws several rays of light from this point to the two sides of the right-angle mirror. Print this card by clicking on the Print Diagram button. You are now finished with the computer and can procede to complete the lab by answering the remaining questions. You will hand in both of the drawings with your lab report.
  3. For each of the ten incident rays heading from the object to the right angle mirror, sketch a normal and use the law of reflection, a protractor and a straight edge to draw the appropriate reflected rays. Be as accurate as possible. Place arrows on all your reflected rays to indicate their direction.
  4. Some of the reflected rays reach the other side of the right angle mirror. For these rays, use a protractor, straight edge, and the law of reflection to show how they would undergo a second reflection.
  5. Once you have drawn all reflected rays (including those which double reflected, use dashed lines to trace each of the reflected rays backwards until they intersect. This is a procedure similar to Part 1.
  6. You should notice that there are three images formed by right angle mirrors. Identify the three image locations by labeling them with a dot on the diagram and then answer the following questions.
    1. Measure the object distance and the image distances for the two images located directly across one of the side mirror. Describe what you notice.

       

       

    2. Draw a line connecting the object and the middle image. What do you notice? Explain.

       

    3. Use words and the diagram at the right to completely describe where the three images in a right angle mirror are located.

       

       

       

 

Conclusion:

Describe how an image is formed, where an eye must look to see an image, and how light travels to the eye in order for the eye to view the object in the mirror. Do a bang-up job!


 

 

 

 

 

 

 

 


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This page created by Tom Henderson and last updated on 8/7/97.