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Materials Needed
Demonstration
- 9 inch (radius) concave mirror
- 400 watt halogen lamp
- wooden stands for the mirror and arm to hold objects (shown right)
- black pen
- matches
- water and/or fire extinguisher
Class Activity
- 3.5" x 16" wooden plank
- two 3" square mirrors
- velcro strips
- double sided tape
Arm (side view)
Arm (front view)
Arm (side view)
1/2
plank copy.jpg
mirror.jpg
plank copy.jpg
1/2
Demonstration Assembly
1. Assemble the mirror with the stand so the face of the mirror is perpendicular to the table
2. Place the halogen lamp approximately 10 inches away from the face of the mirror. Make sure that the lamp is level with the center of the mirror.
3. Turn the lamp on and to find the focal point:
a) take a strip of paper and place it between the mirror and the lamp
b) move the strip of paper back and forth
c) look for a point of light forming on your piece of paper
d) when the point of light is the smallest, that is your focal point!
4. Using pieces of wood, create an arm to hold your objects up to this focal point
5. Make sure all your measurements are precise! If the objects are not held up to the exact focal point, it will be very hard for it to light on fire
Class Activity Assembly
1. At each end of the wood plank, place 2 lines of velcro as shown in the picture (right)
2. For the mirror stand, measure out a piece of cardboard or hard plastic as shown in the picture (right). Fold along the lines and double side tape the last tab to the first. Make sure the bottom tab is at a 90 degree angle to the forward facing tab
3. Using double sided tape, tape the mirror onto the forward facing tab
4. Place velcro on the bottom of the mirror stand to stick to the plank
Note: Small, individual mirrors are often hard to find and may be expensive to purchase. For this activity, I purchased a large 12"x12" mirror and then cut it with a handheld glass cutter.
Plank with velcros
Plank with velcros
*Fold on the dotted lines according to the bottom diagram
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