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Saturday, April 19, 2014

Daily Physics News 04/19/2014

Posted from Diigo. The rest of my favorite links are here.

Monday, April 14, 2014

Mini-Spectrometer... how to build

In this post you can find the links to create this foldable mini-spectrometer.
Here is the video with the steps to create one:

And here is my first picture that I took with my smartphone:

Sunday, April 13, 2014

Daily Physics News 04/13/2014

Posted from Diigo. The rest of my favorite links are here.

Saturday, April 12, 2014

Astronomy Education Alliance Meeting

A message from my friend Rosa Doran:

"Book these dates in your callendar:

September 1st to 5th - GTTP international training

September 8th to 12th - GHOU2014 / Astronomy Education Alliance Meeting

This year our anual meeting (Global Hands-on Universe 2014) will take place in Portugal. This time the meeting is in partnership with some major events. The event will take place in parallel with the Europlanet Science Congress 2014 and in the framework of a major Astronomy Education event: The Astronomy Education Alliance Meeting. The aim is to set the stage to discuss the latest innovative efforts in astronomy education, allowing teachers, educators and outreach professionals to combine efforts and focus astronomy resource production on cross cultural curricula utilizing formal education best practices. 

You can find all information regarding the meeting here:

As already is our tradition we will be hosting during the week before this major event, the GTTP international training. There are special conditions for people willing to attend this training session. All the information can be found here:

We hope that you will join us in this event. We promise this will be an unforgetable experience in sunny Portugal. Some nice surprises are here waiting for you. Please join and spread the word."

I hope you can join us :)

Friday, April 4, 2014

Crookes' work

A Crookes Tube. Credit: Wikipedia
Crookes made a career of being a meteorologist and lecturer at multiple places. Crookes worked in both the fields of chemistry and physics. The salient characteristic of his work was the originality of the conception of his experiments, and his skill in their execution.
His work on electricity in high vacuum, leads us to cathode rays tubes (the technology behind the creation of television).The Crookes tube is an early experimental electrical discharge tube, with partial vacuum, in which cathode rays, streams of electrons, were discovered. The Crookes tube consists of a partially evacuated glass container of various shapes, with two metal electrodes, the cathode and the anode, one at either end. When a high voltage is applied between the electrodes, cathode rays (electrons) are projected in straight lines from the cathode. It was used by Crookes, Johann Hittorf, Julius Plücker, Eugen Goldstein, Heinrich Hertz, Philipp Lenard and others to discover the properties of cathode rays, culminating in J.J. Thomson's 1897 identification of cathode rays as negatively charged particles, which were later named electrons
Crookes tubes are now used only for demonstrating cathode rays.

Crookes radiometer in action. Credit: wikipedia
Another interesting apparatus is the Crookes radiometer, consists of an airtight glass bulb, containing a partial vacuum. Inside are a set of vanes which are mounted on a spindle. The vanes rotate when exposed to light, with faster rotation for more intense light, providing a quantitative measurement of electromagnetic radiation intensity. Today the device is mainly used in physics education as a demonstration of a heat engine run by light energy. 

It is still manufactured and sold as an educational aid or curiosity.
The radiometer is made from a glass bulb from which much of the air has been removed to form a partial vacuum. Inside the bulb, on a low friction spindle, is a rotor with several (usually four) vertical lightweight metal vanes spaced equally around the axis.
The vanes are:
  • polished or white on one side,
  • black on the other.
When exposed to sunlight, artificial light, or infrared radiation (even the heat of a hand nearby can be enough), the vanes turn with no apparent motive power, the dark sides retreating from the radiation source and the light sides advancing.
Cooling the radiometer causes rotation in the opposite direction.
To know more see radiation pressure.
Videos about radiation pressure:

Monday, March 31, 2014


Public Lab Origami Spectrometer

In a earlier post, I published how to build a spectrometer with house stuff. Now, a Physics teacher (friend of mine) show me this great website that show us how to build a mini-spectrometer. You can attach to an smartphone, laptop, or computer with a camera and submit your image to (point your browser to the website and click "capture").

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