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Magic wall(miniture type)

We see a black wall in the center of the box.
There is a hole in the side of it.
We can put our finger into the box.
Do you touch the wall?
No.
Surprisingly our finger pass through the wall without any resistance.
Why?
It is strange that it seems a passing through wall of Doraemon.
In truth, this magic wall is made by the polarization of light.

【Materials】

polarizer glasses for 3D movies
sticky tape
cardboard

【Preparation】

　We use glasses of polarizer with which we see 3D movies in a science museum.
You cut two pieces of polarizer in half.
You turn over one half of the polarizer, and you stick both halves with sticky tape.
You make 2 sets and stick them in the front side and the rear of the box.

【Principle】

　As the directions of polarization are parallel with each other in AA' and BB' sides, light pass through them. But light cannot pass through them in the AB' sides, as the directions of polarization are at right angle with each other.

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Polarization and Eyes of bee

　When light is scattered in the blue sky, scattered light is polarized as the reflected light, when light is reflected from surfaces of water or glass plane. We cannot distinguish polarized light from natural light. But bee's eyes can feel polarized light.
　A bee has compound eyes which are composed of many little eyes called ommatidium.
The eye has four parts showed in the figure.

【Materials】

　polarizer glasses for 3D movies
　Sticky tape.

【Model of bee's eye】

　We use glasses of polarizer again.
When you put a piece of polarizer upon another piece showed in the figure, you can see a dark square in it. Please cut down two dark squares from both polarizers.
　Rotating the square polarizer one by one, you see reflected light on a level desk or on a level plane glass. When you see the clearest reflected light, please cut it down horizontally from 1 to 3.
Please stick four triangular polarizers as showed in the figure by sticky tape, and you will get bee's eye.

【Question】

　When you look in the blue sky with bee's eye, in which direction can you find the difference between light and darkness most clearly?

　Expectation

1. We cannot find any difference in any direction.
2. When we look near the sun.
4. At an angle of 90° from the sun.

　The degree of polarization varies from direction to another.
　Even if you look near the sun, you cannot find any difference between four polarizers. ( Of course, you must not look at the sun itself absolutely. If you do so, you will become blind.)
　You will find the clearest difference between light and darkness in bee's eye at an angle of 90° from the sun.
　A bee can find the directions of the beehive and a flower garden, if it can see blue sky a little.

【Reference】

　"BEES Their Vision, Chemical Senses, and Language" Revised Edition by Karl von Frisch
　Textbook "Light Wave and Radio Wave" The World of Polarizers by Kiyonobu Itakura

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