Polarizing plate experiment 5 barrage: Making a polarizing microscope, rock preparation, equigranular structure, making a polarizing plate, making a polarized kaleidoscope
Experiments with polarizing plates are very colorful and beautiful. Through the experiments, I will introduce these experiments as a chance to know how the polarizing plate is actually useful for daily life.
Experiment 1: Let's make a polarizing microscope
I would like to show the rock preparation to the students once using a polarizing microscope. All you need is a polarizing plate (8 cm square, several hundred yen)! The original use of a polarizing microscope is to identify the composition of rocks and to investigate the strain of the crystal structure of plastics. Here, we will only say that the color changes depending on the type of crystal and the difference in making.
you need : Polarizing plate, rock preparation, microscope
Cut one polarizing plate into a circle. Put it in the eyepiece. Place the other one under the rock preparation, and then rotate the eyepiece while looking under a microscope. Of course, a more decent microscope is needed to identify minerals. However, isn't it enough to experience the mechanism of a polarizing microscope?
Experiment 2: A substitute for rock preparation
Sometimes there are sites that show you how to make rock preparations. However, it is technically difficult to make. Previously, thin rocks were made considerably thinner with metal files and sandpaper, but it is difficult to put into practical use. Therefore, urea crystals are used instead.
you need : Polarizing microscope, concentrated urea solution, glass slide
Apply a thick urea solution to the slide glass with a glass rod. When it turns into a crystal, it is examined under a microscope.
Experiment 3: Let's investigate the difference in crystal size between volcanic rock and plutonic rock with urea crystals
you need : Polarizing microscope, concentrated urea solution, glass slide
Add a small amount of concentrated urea solution to the petri dish. One is chilled with water and the other is chilled with hot water. Those who cool slowly with hot water will have larger crystals. However, this experiment is highly dependent on the concentration and amount of urea solution. I think it's better to present what you've done well, not student experiments.
Experiment 4: Let's make a polarizing plate
you need : PVA glue, plastic sheet, iodine solution, cardboard, cellophane tape
Dry the PVA glue on a plastic sheet. Cut the dry PVA into 8 cm squares. Soak in iodine solution to soften. Pull and stretch 3-4 times in length. Let it dry as it is. Paste it on cardboard and you're done.
The photo on the left shows the polarization axis (slit direction) in the same direction, and the photo on the right shows the rotation by 90 °. There are some aspects that are not suitable for detailed experiments, but it is still best to show the real thing in the explanation of polarized light. I would like to bring PVA glue overseas as well, as it is recommended when conducting science education with overseas support.
Light is a wave that vibrates with electromagnetic waves. In that light, the polarizing plate allows only light that vibrates in a certain direction to pass through. Look at the picture on the left. The polarizing plate of A allows light of vibration in the vertical direction to pass through. B allows only the light of lateral vibration to pass through. By shifting the vibration direction by 90 ° in this way, the light can be completely shut out. Using this property, characters and pictures can be projected on the screen of a TV or PC by allowing light to pass through or not.
Experiment 5: Let's make a polarized kaleidoscope
you need : Polarizing plate, paper cup, cutter, cellophane tape, plastic
Attach the polarizing plate to the paper cup. Draw a simple picture on a plastic plate with magic and stick cellophane tape on it in several layers. Make the thickness different depending on the location. Cut out along the frame of the picture.
Place the picture between the two paper cups and rotate the paper cup. In this way, polarizing plates allow you to see the strain of a substance depending on the difference in crystal structure, thickness, and how force is applied when it is made. The last photo shows the handle of the hand mirror sandwiched between the polarizing plates. You can see how the force is applied when it is made. Using this property, it is used for quality control of materials and products, sugar content meters, etc.