Itzá demonstrates classic light experiments for students in Mexico

Release Date: 7/19/2013

It was 8 a.m. on a Thursday morning, and Dr. Salomón Itzá, associate professor of physics at Ozarks, had the Smith-Broyles Science building pretty much to himself. He sat at a table in the physics lab with his iPad, entering a phone number into Skype. It took a few attempts, but the number finally connected. "Buenos días," Itza said with a broad smile.

"Buenos," came the answer from a man on the other end of the connection. Sitting behind the man was a group of students, who cheered and waved to the camera. The students were in Mexico, at a private bilingual high school affiliated with the Presbyterian Church of Mexico, and their physics class with Itzá was now in session.

The Director of the high school was a friend of Itzá's from college. The plan, Itzá explained, was to use Skype to communicate with the school in Mexico. "[H]e will bring it onto a screen in a classroom, and I will be in one of the physics labs so I can show the students a couple of experiments that we do for the physics labs here at U of O," he said.

With the introductions finished, Itzá gave the students some background information about the demonstrations they would see that morning.

The first was a modern version of an experiment first performed in 1801, by Thomas Young, called the "double-slit experiment." Itzá explained how Young had come to believe that light travels in waves, but his ideas were rejected by his peers. So he set out to develop an experiment to test his theory. In his "interference experiment," Young passed light through two parallel slits. The result was a pattern of light and dark patches on a screen on the other side, corresponding to the points where the peaks and troughs of the waves combine with each other, either constructively (the light patches), or destructively (the dark patches).

Itzá then turned off the lights, and carried his iPad over to the table where the equipment was set up. Carefully, he positioned the camera behind the small green laser so the screen behind the slit was visible to the students. "Can you see?" he asked them. "Yeah!" they responded enthusiastically. There on the white paper were the dark and light patches, just as Young had observed. How could physics explain this?

Light Experiment

Itzá shows the students in Mexico the effect of Young's light experiment.

Turning the lights back on, he took the iPad to a chalkboard where he had previously written out several mathematical equations. Holding the camera so the students could see the different board, he described how the double slit disrupted the light beam and how the equations explained what they had just observed.

Itzá next pointed the camera at a white board, on which he had written the letters "R O Y G B V." What did they mean? He turned off the overhead lights again, and then shined a light from small lamp on the desk through a prism. "What do you see?" he asked them. "Rainbow!" they exclaimed. Yes, Itzá said, it was a rainbow, and it showed that light is really composed of different colors, each with its own wavelength. "Red, Orange, Yellow, Green, Blue, Violet," he said pointing to the letters written on the board.

This led into the next demonstration, an experiment done by J.J. Thompson in the 1800s using a cathode ray tube. Thompson is credited with discovering electrons and isotopes, and for inventing the mass spectrometer, a device which shows the spectra of the masses of molecules in a sample. Itzá showed the students some PowerPoint slides describing the physical principals behind mass spectroscopy, and showing how the light from different sources produces unique bands of colors.

Light Experiment

What the students observed can be described by mathematical equations, Itzá explained.

The students eagerly asked questions, and Itzá answered, moving the iPad camera from the slides to the demonstration equipment on the lab table. As their time ran short, Itzá finished by telling the students about some of the opportunities they could find if they wanted to continue studying physics. The students asked Itzá to take a picture of their class, and he held up a small digital camera snapped a picture of the iPad screen as they waved goodbye.

Outreach demonstrations like this are something Itzá enjoys doing...it allows him to share his passion for physics with students even outside the classroom. It was his second demonstration this year - the first was a presentation on rainbows at a local pre-school. But Itzá confessed to being a bit apprehensive about doing this demonstration. It was his first physics demonstration presented entirely in Spanish.

"I don't know how to write some of those words in Spanish," he said. "I don't even think I can pronounce them, because I've never taught physics in Spanish!"

Itzá presented one other demonstration over the summer - "Rainbow Spectacular" - at the Johnson County public library, as part of the library's summer reading program.  He hopes to do more outreach demonstrations as time permits. So if you happen to be curious about why there are sometimes rainbows in the sky when it rains, or how light can be used to identify something, keep an eye out for announcements about Dr. Itzá's demonstrations. "It's fun, just getting ready for them!" he said.