With the Light and Sound exhibit, you will get to know the differences between light and sound waves. You will see what happens to them in the air and in a vacuum.
In the air, i.e. in the state you know, you can see the light of a bulb and hear the sound of a bell every day. After the air is pumped out, i.e. in a vacuum, you can see the light but the sound becomes inaudible. Sound waves need a medium to propagate, so there is no sound in the vacuum. Therefore, scenes from science-fiction films which feature loud explosions in the space are false. There is a vacuum in the space and, thus, an overwhelming silence!
1. Technical problem: the bell often breaks down
Solution: design a better bell
A regular doorbell is not used very often: maybe from a few to a dozen or so times a day. But the one installed in the Light and Sound exhibit rang at least a thousand times a day! It turned out that no household doorbell manufacturer had designed for such an intense doorbell use as in the crowded Copernicus Science Centre. We had had to repeatedly replace the device until we substituted it with a brass ship bell, which was stronger and more durable. In addition, we developed a special hitting device – a “magnetic woodpecker”. The sound is emitted in the bell as a result of it being hit strongly by the device.
2. Scientific problem: when the surrounding area is quiet, it turns out that the bell is audible, even though the air has been pumped out of the shade and there should be a vacuum inside.
Solution: Analyse the finest details of the design and eliminate imperfections.
True measurements differ from tasks solved on the whiteboard in that they are always burdened with the error called measurement uncertainty. Such a situation was created by the new ship bell. So, we tried to minimize the error. It turned out that the new brass ship bell was stronger and louder. Immediately after installation, it was so active that it rang due to the sound being transmitted through the exhibit structure. We wondered how to deal with this problem and decided to hang it on springs. Now it works as intended.
3. Problem with difficult observation: when there is loud noise around, you cannot hear the bell.
Solution: change the design of the exhibit while ensuring that safety requirements are met.
When we have a lot of visitors, it is loud. You cannot hear the bell well and it is hard to see the differences between the light and sound waves. We wondered how to change the design of the exhibit to make the sound stronger. The bell and the bulb were placed under a shade, above which there was a safety shield made of plexiglass. We decided to use only one shade so as to make the sound louder. But what should it be made of? At first, we tried the plexiglass. Unfortunately, although this material can be nicely joined together, it shatters into small sharp pieces when broken. In the end, we built a polycarbonate shade because it breaks into two or three large pieces, thus in a safe way.