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In Modern Physics, we talk about how the Braggs used x-rays to determine crystal structure. In lab, we don't use x-rays because of radiation damage. Instead we duplicate the classic experiment using low-power microwaves with "crystals" made of ball bearings. Usually we hold the bearings in position using foam as seen in the picture on the right. This year (after the lab was completed using foam holders), we started building up ball bearing holders using plastic. The plastic does mess up the microwaves a bit, but it allows us to change the crystal size really fast. The crystal on the left has holes cut for bearing spacings of 3, 3.5, 4, and 4.5 cm. A laser engraver was used to make the pieces. In time for next year's lab, we will have a number of these sets made.
Normally during October we have labs in all the big classes where we take air rockets out to the field and learn about projectile motion. Since all those classes are on-line this quarter and it doesn't seem fair to have a fun lab with no students invited, we did a lab on projectile motion based on shooting a ball from a spring. Because the ball only goes about 2 meters - instead of the 65 meters for the rockets - the lab is a lot less exciting, but it does give much better results. In the graph, the rocket data is all over the place because we have to deal with wind, variation in launch pressure, and human uncertainty in identifying the exact landing location. The ball data is almost a perfect parabola since taking the data via video in a room without wind minimizes many of the noise sources. (In the graph, the ball distance data was multiplied by 30 so both data sets fit on the same graph.)
Moral: Distance learning isn't as fun but it can be more accurate.
School is back in session for the 2020-2021 year. Because covid-19 is still with us, many of the sophomore and junior classes are remote. General Physics and Principles of Physics are on-line so the labs are mostly done by watching videos of the experiments. In the picture at the left, we are measuring the height of Kretschmar Hall by dropping a golf ball from the top and measuring its time of flight. One advantage of the video lab is that the camera is much more accurate with timing than a human using a stopwatch.
In a number of labs from Conceptual Physics all the way to Modern Physics, we look at spectral lines from various gasses. Normally, the data is analyzed on the same program that was used to collect the data. During the remote learning last quarter, it became obvious that not all students had the necessary hardware to run the main program so they couldn't analyze the data fully.
This summer the Physics Department gratefully received a donation from the Fluke Corporation. The multimeters and thermocouple therometers will be used in the large introductory labs such as General Physics and Principles of Physics. The Fluke Corporation routinely makes such donations to colleges in the Northwest. Thank you.
Sometimes when looking at news items like this article on dark matter, https://www.cnet.com/news/dark-matter-detector-picks-up-unexpected-and-unexplained-signal/, one might click on the link to the original article, https://arxiv.org/pdf/2006.09721.pdf. This article is a bit more interesting than some because one of the authors/researchers is a graduate from the Physics Department at Walla Walla University. Darryl came back to WWU and gave a talk about this experiment several years ago. It is exciting to see the progress that the team is making.
While our labs are still on-line for the quarter, we are continuing to see improvements in data collection by using cameras as I mentioned last month. So far this quarter, we have gotten excellent data for the thermal expansion of metal tubes in General Physics and Principles of Physics Labs and in the temperature dependence of semiconductors in Physical Electronics Lab. Also in Physical Electronics Lab, we set a department record for the most voltage generated by a solar cell that we built. In the picture at right, the cell is in the upper right of the picture with all the gold "fingers" making electrical contact to it. While 0.183 V may not seem like much compared to the 0.5 V that a commercial cell generates, it is much better than the 0.025 V that our previous build process produced.
This quarter, Walla Walla University like nearly all other schools is meeting on-line only. Our labs are on-line as well. This means the experiment is recorded and the students watch the video and collect data from the video. In the picture at left, a screen capture from a Principles of Physics lab is shown. A stream of electrons is hitting some helium gas and making the greenish glow. From the measured parameters, we can compute the ratio of the electron charge to the electron mass.
The interesting thing is that using cameras to collect data in many situations gives better results than the data collected by eye only. Some labs are being rewritten to suggest that the data be collected by cameras always.
Most universities in the US (and many around the world) are on-line only starting this month to limit the spread of Covid-19. Walla Walla University is among that number which means the WWU Physics Department is working on ways to delivery lab classes remotely. While there is some variation in our labs, our basic idea is to record a video of the experiment being run. The video will allow the students to collect the data from the equipment and to do the analysis steps as normal. The only missing step from doing the lab in person is the setting up of the equipment. While we realize this is inferior to the hands on approach, it is the best solution we have right now.
For another experiment in nanotechnology, we have been working with graphene. This experiment starts with graphene oxide in water. The solution is put on a piece of filter paper and allowed to dry. Once it is dry, it forms an insulating brown layer. Then we expose part of the layer to light and convert the graphene oxide into graphene which conducts. This allows us to draw circuits on the paper as shown in the picture.
The new quarter has started and Introduction to Nanotechnology is underway. The first two labs of the quarter are spent building a scanning tunneling microscope. As shown in the picture PVC and hot glue play a role in the construction. Four lab groups are each building up their own microscope. The detailed build directions from the 2014 article are available at https://www.wallawalla.edu/academics/areas-of-study/physics/faculty/ekkens-research/studentstm/ . Over the last six years, we have made several changes in the design to make use of our 3d printers. An update to the build directions should be finished by this summer.
Our Christmas break has started early this year so we didn't take any fun pictures during the month. We will be back on January 6, 2020 for another exciting quarter.
In Modern Physics lab, we measure the speed of light. Over the past several years, we made a number of improvements to the lab by getting different lasers, reworking the detector, and switching the mirror material. This year we designed a mounting system for each of the parts and built them using a 3D-printer. In the picture at the right, the PLA material is the white housings that hold each of the major parts. These new parts don't improve the data but they do make the lab much easier to do.
Each fall during the Modern Physics Lab, we spend some time learning to use the scanning electron microscope. This was the first year that a 2mm spider was used as the sample. In the picture at left, several students are looking at the spider's elbow. This was also the first year that significant time during the lab was spend on studying the impact that different accelerating voltages and aperture sizes had on the images.
About a year ago, we purchased a cheap cloud chamber kit made from a plastic container that ran on dry ice. The region of where the tracks were visible was fairly small. This summer we purchased a larger system that uses regular ice (and a chiller). This one will be used in several classes both for demonstrations and to collect actual data. The working area is about four times bigger than the previous system.
This summer Cody completed the drive system for Mossbauer spectroscopy system. Adjustments will continue to be made before it is implemented as a lab in Modern Physics II. In the picture at the left, the detector is at the bottom of the picture and the drive is at the top.
Cody then moved to a computational project to study Lattice Quantum Chromodynamics through an open source program called Chroma. While statistically significant results would require the computing power of a supercomputer, we hope to run single test simulations to better understand the program in hopes of collaborating in the future.
This summer we have three students working on undergraduate research projects here at WWU. Most of the projects are continuing from last summer. Last summer, Heidi and Jeff worked on the Raman Spectroscopy system. They 3d-printed almost all the parts, soldered together the electronics, and started looking at the software. This summer Felicia is going through the software to make sure each component works correctly. In the picture at the right, the two major control boards are on the right and are driving the motor in the foreground.
The 2018-2019 school year is now behind us. It was a record setting year for the physics department. On June 16, 2019, eight physics and biophysics majors graduated. This is the highest number of graduates in a single year in the history of the WWU physics department. The previous record was seven graduates each in 1961 and 1966. The seven physics majors are shown in the picture.
Each spring in Physical Electronics, we cover how solar cells work. In lab, we take solar cells outside and measure their current and voltage characteristics as a function of resistive load. We also measure the response to diodes that we have made in lab. This year our diodes didn't give very much voltage when they were in the sun.
The “Mechanical Equivalent of Heat Apparatus” device from Pasco is used in many of our lower division labs. The device works very well and gets good results, but the counter sub-system is prone to failure. It consists of a small rubber tab on the handle and a mechanical counter. Each time the rubber pushes on the metal finger of the counter, the mechanical counting system advances by one. The rubber and the metal finger both break over time. Dr. Campbell suggested using a magnetic system instead. A magnetic counter was purchased from Amazon and several parts were 3D-printed to hold the system together. In the picture at the left, the upgraded system is on the left and the original system is on the right. The upgrade process has been passed on to Pasco.
The artwork refresh in the entry to the lecture hall is completed. The old pictures were faded by the sun and the light boxes were not working. Facilities services removed the broken hardware, patched, and then painted the walls. Dr. Campbell ordered the new artwork and hung them in position. The top picture is from the left entry into the lecture hall and the bottom picture is from the right entry into the lecture hall. The placards from Dr. Campbell read (top to bottom):
Stephan's Quintet: A visual grouping of five galaxies in the constellation Pegasus discovered by Édouard Stephan in 1877. Four of the galaxies form a compact galaxy group. The brightest member of the visual grouping has extensive regions, identified as red blobs, where active star formation is occurring.
Cassiopeia A: The remnant of a massive supernova explosion that occurred approximately 11,000 light-years away. The expanding cloud now appears approximately 10 light-years across. This is a false color composite image from three sources: the Spitzer Space Telescope (infrared), the Hubble Space Telescope (visible), and the Chandra X-ray Observatory.
The Crab Nebula: A Hubble image of the remnant of a massive supernova explosion in the constellation Taurus. The explosion was seen from Earth in 1054 AD, and was bright enough to be visible in daylight for 23 days. The Crab Pulsar, a neutron star 18 miles across spinning 30.2 times per second, lies at the center of the nebula.
The Great Orion Nebula: An infrared image of the star formation region obtained from multiple exposures at the European Southern Observatory. The nebula is a stellar nursery where new stars are being born. Approximately 700 stars are in various stages of formation within the nebula.
As the quarter continues, so do the optics labs. So far, we have studied interference, polarization, and diffraction. The picture at the right shows diffraction pattern from a razor blade. The math for this diffraction pattern is more complicated than the math for the single and double slits. We have used the red lasers for more labs but the camera picks up the green laser better so it gets used for all the pictures.
This quarter we are teaching optics and its lab. The picture at the left shows the setup that we used to determine the index of refraction for a glass microscope slide. We are starting to merge the expensive world of precision optics with the cheaper world of 3D printing. In this setup, the holder for the microscope slide is 3D printed while the rest of the setup is very precise.
December is a busy half month. In the Physics Department, we set up the Christmas tree, had the annual Christmas supper with the majors, listened to or participated in the WWU Christmas Concert, had final tests, and gave or received grades.
By the middle of the month, all the loose ends are tied up and many of the students and teachers have left for vacation. The campus is quiet and waiting for the start of the next quarter.
During the early part of Modern Physics this quarter, cloud chambers were mentioned. They will be covered in more detail in Modern Physics II. This year we purchased a Thorium Lantern mantle to use as an alpha source so we used it as a demonstration in Modern Physics Lab.
This chamber is built the easy way. Dry ice is underneath the plastic box and the alcohol vapor is contained in the box. The thorium mantel is the white and pink piece in the upper portion of the image. The vapor trails are visible against the black plastic. Click on the picture at the left to get a video of the chamber in action.
This time of year, the trees outside the physics department are very colorful. The picture below at left is just outside the department office. Inside, the Modern Physics class is studying electron motion. As part of that study we use a scanning electron microscope to take pictures of several things - including the fruitfly below at right. Electrons don't have color so that picture that they create is just shades of gray. The magnification in this image is 35x.
Our 2018 - 2019 school year started with the Jumpstart session (and the Jumpstart supper) when we welcomed the new majors. A few classes have happened and work hours are assigned. Even some assignments are coming in. We are excited about the possibilities of the new year.
The Walla Walla Physics Department is enjoying a period of growth as seen in the chart below. For this year and the past two, we have the highest number of majors in recent history. We had a record number of student research projects over this past summer and recent graduates are going to good schools.
Another project for student research this summer is the Mossbauer System. This project has one student working on it with the goal to use stepper motors to shake a radioactive sample at exactly the right velocity. The starting place for the mechanical system was an old 3d printer bed.
This summer we have several research projects going on that are focusing on building new hardware. The Raman Spectroscopy project has two students working on it and is following the ramanPi instructions on Hackaday. So far, most of the month has been spent printing parts on the 3D printer (shown in the picture at right) and building up the electronics.
As part of the Modern Physics 2 class, we took a field trip to see some of the large science projects in our area. The first stop was the B Reactor at Hanford. In the picture - below at left - our class is standing in front of the reactor pile. The next stop was LIGO. The picture below at right has us posing in front of one of the interferometer arms.