Archiv für den Monat: Februar 2022

Welcome to the new category „ScienceNews“!

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First of all: A warm welcome to the recently introduced category „ScienceNews“!

Due to the wide range of scientific news provided by different more or less serious webpages where several authors with a different level of knowledge and experience can publish stories they consider to be worth reading them, we decided to set up a new platform as a subpage of the ScienceBlog that we called „ScienceNews“.

On that platform, we would like to release articles that explain current scientific events (for instance the start of a new innovative rocket to discover the planet Mars or a breakthrough in reusing emitted warmth to slow down the climate change) in a way that not only experts, but also „common“ people that do not have any special pre-knowledge are able to understand and follow the most significant points. For illustration, we will attach some photos and graphics that deepen the understanding of the processes in the background (which are often even more interesting than the event itself) that enable the readers to get curious and make them wanting to find out more. Therefore, we will give credit to the sources and add some links referring to additional information at the ending of each post.

As we have got a few motivated and enthusiastic writers, our articles will be provided either in English or in German.

In case you have got ideas or improvements, we are happy to receive a message in order to fulfill our aspiration of getting better every day according to our slogan „You are always a student, never a master. You have to keep moving forward.“ (Conrad Hall, photographer and filmmaker).

We hope you appreciate our well-researched articles as much as we do. Enjoy reading them!

written by Michael Himmelbauer (in representation for the whole ScienceBlog team)

The shoebox speaker

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written by Michael Himmelbauer

By using a common shoebox, enjoyable music with a high sound quality can be played. What sounds to be unimaginable, can be realized with some components you may have at home, but can also be found in the physics room:

  • an amplifier (the older the better)
  • two cables
  • a magnet (the stronger the better)
  • a coil (or a long piece of wire and a cylinder (for example from toilet paper))
  • the star of the experiment: a shoebox (without the cover)
  • a device with a plug to play music
  • and of course: enjoyable music (for instance on your mobile phone)

First of all, you have to glue the coil (or the wire wrapped around the cylinder) onto the bottom of the shoebox. Furthermore, the cables have to be plugged into the amplifier (take care that you use the correct ports) and have to be connected to both of the ends of the coil (no matter whether it is bought or a self-made one) as shown in the pictures:

Moreover, you have to select a relaxing song to play (due to the wide range provided on the internet, this could be the most difficult part of the experiment). In order to broadcast the music, you have to connect your mobile phone, computer or MP3-player to the amplifier (either via another cable or wireless). As soon as you have started the song, place the magnet in the middle of the coil as shown in the picture:

In case you read the instructions carefully and the cable connection works, you may be speechless at that point as you can hear your favorite song without using a classical speaker (or headphones).

But why’s that? Why can music be played without using speakers?

Admittedly, the shoebox works as a speaker as the mantle of the cuboid replaces the membrane.

In order to understand that phenomenon, we need to take a look at an electro-magnetic force named by the physicist Hendrik Antoon Lorentz. It occurs as soon as a current flows through a conductor. Its direction has an angle of 90 degrees to the direction of the flow and the magnetic field.

And as the amplifier dispenses alternating current (AC), the direction of the flow inside the coil changes constantly and that is why the direction of the Lorentz force changes, too. Subsequently, as the magnet remains at the same place, the coil swings back and forth with the frequency of the flow (that the amplifier dispenses). As a result of that (the coil is sticked onto the bottom of the shoebox), the membrane swings with the same frequency. Moreover, the swinging membrane spreads waves into the air that get to our ears where they are converted into an electric signal that is forwarded to the brain (ask a biologist if you’ve got any questions concerning the processes inside the human body).

To convey the theory more easily, I made a drawing that outlines the effects of the currency to the coil and depicts the formation of the acoustic waves:

In case you are curious, you could also use the speaker for playing spoken records (for instance a speech from a well-known politician or the latest news program). While listening to the wisely chosen words from a famous person, you may be amazed by the high quality and the clear sound.

Another usage of the self-built speaker could be its opposite, a microphone. When recording waves, the Lorentz force is considered to move the electrons inside the wire and that is the reason why an electric voltage is induced (to try that, you could conduct an experiment on your own that is similar to the described one).

To sum up, it can be mentioned that with the help of a shoebox and some other components, but without a speaker, music can be played and quite some things can be found out about the characteristics of the acoustic waves that enable us to understand each other properly.

source:
Putz, Bruno; Jahn, Brigitte: Faszination Physik 7 bis 8. Lehrplan 2018. Linz: Veritas 2019, p. 13

fotocredit: (c) by Michael Himmelbauer

one laser pointer, nine rays

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written by Michael Himmelbauer

A usual laser pointer emits one ray, but nine can be seen on the wall after the ray passes a special optical instrument. What sounds to be impossible, can be realized with the help of some components that you may not have at home, but fortunately can be found in the physics room:

  • a laser pointer (for example a green one)
  • a bar grid
  • two tripods
  • for measuring: a measuring tape

First of all, you have to set up the components as shown in the picture, preferably in front of a white wall in a rather dark room.

When you switch on the laser pointer, you may be surprised by the fact that you can see nine rays on the wall, although only one ray is emitted by the laser pointer. At that point, you might want to ensure that it works properly, but please do NOT look directly into the light of the laser pointer for safety reasons (at least if you don’t want to damage your eyes forever).

Now you may ask yourself: Why’s that? Why can nine times as many rays be made out even if only one is emitted?

Therefore, we need to take a look at the structure of the bar grid. It consists of several lines into horizontal and vertical direction printed onto a disc of glass. The label „200 lines per millimeter“ means that there is a space of 0.000005 m between each of the lines.

For simplifying the process, we need to assume that the bar grid doesn’t feature several, but only two gaps (with the same width as above). When an electromagnetic wave passes these gaps, it turns from a straight to a circular wave. After that, the amplitudes of the waves interfere with each other, and those interferences are spread until they get to the wall. There, they are reflected and the light (again in the form of waves, but with a much lower density) gets to our eyes.

For illustration, I made a drawing to convey the theory:

The next question that comes to your mind might be: Can this theory also have benefits when using it in a practical way?

As a scientist, I say: Yes, it can. For instance, we can take usage of it when calculating the wavelength of a specific color (and that’s the reason why we conducted this experiment).

For simplification, we have to estimate that the sine of a small angle is has almost the same value as the tangent of the same angle (supported by the fact that for angles like that, the cosine is almost 1 and the tangent is calculated by the quotient of sine and cosine).

According to the drawing above, we can make up the following equations:

And as we are able to measure the distance from the tripod to the wall (2.08 m), the distance of the lines on the bar grid (0.000005 m) and the space between two points on the wall (0.225 m), we are able to do the following calculations easily:

That means that the light of the green laser pointer we used in the experiment has a wavelength of approximately 541 nanometers.

Another practical application of the effects of interference is used in clubs for the disco lights, featured with a small engine that slowly rotates the light emitting diode (LED). That is why some impressing patterns can be seen on the walls and on the ceiling.

To sum up, it can be mentioned that with the help of a laser pointer, a bar grid and two tripods, the wavelength of a specific color can be calculated and quite some things can be found out about the spreading of the electromagnetic waves that light up our everyday life.

source:
Putz, Bruno; Jahn, Brigitte: Faszination Physik 7 bis 8. Lehrplan 2018. Linz: Veritas-Verlag 2019, p. 68-69

fotocredit: (c) by Michael Himmelbauer

The liquid powders

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written by Michael Himmelbauer

Firstly, you put a few grams of two white powders into a beaker and after stirring for a minute, it turns into a turbid liquid. What sounds to be impossible (or fake news, as we would call it), can be realized with the help of some components you may not have at home, but luckily can be found in the chemistry room:

  • two beakers
  • a spoon
  • a scale
  • a brick of wood
  • the stars of the experiment: 15 grams of Barium hydroxide (Ba(OH)2) and 5 grams of Ammonium thiocyanate (NH4SCN)
  • some water (H2O)

First of all, we weigh the required amount of the two powders with the help of the scale and put them into the two beakers as shown in the picture:

Next, we do something you better should not do if you don’t know what’s inside the beakers (fortunately, I know what I’m writing about): We pool the two powders into one beaker (in case you’ve got two different sizes: put it into the bigger one) and mix them with the help of the spoon. After some time stirring (and maybe a hurting arm), we recognize that inside the beaker, the powders disappeared and were replaced by a turbid white liquid. Furthermore, the fluid smells strange. In case you touch the bottom of the glass, you may find out that it feels cold (although the windows and the fridge are closed, so the cause of the low temperature is the beaker – even if you don’t believe it).

But why’s that? How can two powders that look almost similar turn into a liquid that stinks and cools down its environment?

To explain that chemical process, we have to take a look at the reaction equation of Barium hydroxide with Ammonium thiocyanate:

Ba(OH)2 + 8 H2O + 2 NH4SCN → Ba(SCN)2 + 2NH3(g) + 10 H2O

According to the equation, the educts Barium hydroxide (that consists of Ba(OH)2 and solid water (H2O)) and Ammonium thiocyanate (NH4SCN) react with each other. The products on the right side of the equation are Barium thiocyanate (Ba(SCN)2), Ammoniac (NH3) and liquid water (H2O). The turbid liquid consists of Barium thiocyanate and water, Ammoniac is released into the air as a gas that causes the unpleasant smell.

And in case you put the beaker onto the wept brick of wood, you might be frightened when you want to lift the glass because you may recognize that the ice-cold beaker sticks onto the brick of wood:

But why can a liquid that consists of two strange powders make a glass stick on a wooden part?

In order to answer this question, we have to know that the chemical reaction described above is considered to be an endotherm reaction as energy (in the form of warmth) is required all the time. This energy is taken from the environment around the powder in the glass, and that is why the glass cools down. And as we all know (or have at least learnt at school), water freezes in case the temperature drops below zero degrees. Caused by the fact that we put some water onto the brick of wood before mixing the powders, the breaker has frozen onto it.

The energy graph (a diagram that shows the amount of energy a substance contains) of an endotherm chemical reaction outlines that the products in the end have a higher level of energy than the educts at the beginning. In order to compensate the difference, energy in the form of heat is required and is taken from the environment.

To sum up, it can be stated that when pooling two special powders into one beaker, their state of aggregation turns into liquid and the required energy can make the glass freeze onto a brick of wood. Both are results that wouldn’t come to your mind when you’re thinking about powders, would they?

source:
Anon.: Entropische Zauberei. https://www.uni-wuerzburg.de/fileadmin/08020000/pdf/erlebnis/endotherm_reak.pdf
[last access: 01.02.2022]

fotocredit: (c) by Michael Himmelbauer