Magic Cylinder and Part 3 of Reflection Lab (Curved Mirrors)

If you missed today in either 2012-2013 or 2013-2014 a makeup lab is in the back resource area for makeup:

1.  Students walked around the classroom looking at dozens of past magic cylinder examples (these are really cool, take a close look at each)

example 1        example 2        example 3        example 4        magic cylinder blank1     magic cylinder blank2

After looking at an example you'll see you want to draw your picture in the small square box at the top of the blank and then note the lettered (A,B,C,...) row and numbered (1,2,3,4,...) column of any given square and draw the similar shape in the same curved rectangle in the bottom grid.  When you set a curved mirror on the paper  between the pictures you made, your original picture will show up in the curved mirror.

Note:  If you wish to make a curved mirror, we just got some aluminum foil (or that reflective Christmas wrapping paper) and taped it around a pvc pipe a few centimeters longer than your reflective foil is wide (so you can lift the pvc pipe without getting your finger prints on the foil.

The Magic Mirror is an assignment worth 5 points (for a  simple one) due next Friday BUT if you do one like in the examples above (in color with curves) you can receive up to 5 pts. extra credit on it!  Happy drawing!!!  :)  :)  :)

2.  We demonstrated how concave and convex mirrors work on the white board for part 3 of yesterdays lab in 2012-2013

Here is part 3 Curved Mirror explanation showing how parallel rays of light reflecting off a concave mirror all reflect through a very special point called the Focal Point which is the focal length away from the curved mirror along the principal axis.  Here is the Reflection Lab handout again.

Here are examples of part 1  and part 2 and part 3 concave side and convex side done by students who finished and turned in the lab today from 2012-2013 school year.

2.  In 2013-2014 either one lab group volunteered to do their part 3 on the Elmo so the rest of the class could do theirs simultaneously with them while they were instructed by me or if enough lab supplies I did the lab on the Elmo as students in groups of two completed theirs.
Here is an example of mine for the concave mirror note that:
1).  Toward the top of the blank sheet of paper (because the focal point and center of curvature are both found on the concave side or front side of the mirror) we traced the concave side of the mirror first. 
2).  We drew the cord with vertices at the ends of the curved mirror.
3).  We constructed the perpendicular bisector of the cord and labeled it the principle axis.
4).  We placed a straight edge (we used the protractor but the plastic ruler could have been used) to help trace two more parallel lines on each side of the principle axis.  We numbered the five parallel lines 1, 2, 3, 4, 5.
5).  One lab partner held the laser light along each parallel line while the other partner tipped the top of the curved mirror forward until the reflected ray could be seen so the person tipping the mirror could place a dot in the center of the reflected beam and number the dot the same as the incident parallel line was numbered earlier.  Repeat until all five reflected rays are dotted and numbered.
6).  Now the mirror could be removed and all the reflected beams drawn from the intersection with the mirror and the numbered dots.
7).  The focal point is labeled where the majority of intersecting five lines meet and the focal length is measured to the mirror.
8).  The focal length is doubled which becomes the radius of curvature of the mirror and the point C is labeled on the diagram (which is the center of curvature of the mirror).  Note that f=r/2 always.
9).  All the above steps are repeated for the convex side only now start the mirror toward the bottom of the blank sheet as the Focal Point and Center of Curvature will be behind the mirror.  Looking at last years example for the convex mirror has mistakes as the Center of Curvature (C) is not in the diagram.
10).  Place a purpose and conclusion on each diagram and answer all six questions and turn in by next Wednesday in 2014 (April 23rd) with all four sketches, and questions stapled neatly with all lab partners names on the front top right side.

The Big Picture:  Note that all satellite dishes are the concave shape as light signals from space come from so far away that they enter Earth as parallel beams of light.  Now all we have to do is place the collector of the information facing the dish at the focal point which will be located at the midpoint of the radius of curvature of the mirror along the principle axis.  Thing about it and note this on all the dishes.