May/June 2017 – Vol. 29 No. 7

The Teaching Length Scale

Posted: Tuesday, May 6th, 2014

by Galen T. Pickett

Physics can be organized by the size and duration of events. When we teach Newton’s mechanics, the examples we use typically are on length scales of meters and on time scales of seconds (tossing a ball, sliding into second base) and run up to solar system scales (tens of millions of kilometers for an Astronomical Unit, and tens of millions of seconds for a year). But, unless your classroom is equipped with technology at the extreme ends of the sophistication scale (chalkboards at the primitive end, and SmartBoards at the super-fancy end), you probably use ordinary whiteboards and erasable marker to make sketches and calculations for your students. The marks you make on this surface meet some basic criteria: they have to be wide enough (half a centimeter or so) to be clearly seen from every vantage in your room and they have to strongly absorb visible light – making a visibly saturated mark. The width of the marks is controlled by the properties of the pen tip, and the saturation of the marks is controlled by the pigment in the marker, but there is another, often overlooked length scale in your markings.

Advertisement

Advertisement

What is the thickness of the marks? It can’t be zero, and it can’t be on the order of millimeters (you can easily feel roughness on the scale of tenths of millimeters with your fingertips, the width of a single human hair). What I have below can be organized into a demonstration or a full experiment supporting topics in waves and optics.

  • Have a supply of “wet” whiteboard markers on hand. A couple of different colors if you are doing a demonstration, enough for each group to have one if this is a class-wide exploration.
  • Make several marks (or have your kids make marks on their whiteboard slabs), different orientations, curly-cues, some nice cursive if you can manage it, ask for what length scales your students observe.
  • Ask about the thickness of the marks … how far from the surface of the whiteboard do they jut?
  • Use a web-camera and a second light source to show what the marks look like up-close. Make sure you can see the marks “through” the reflection of your light source.
  • If you see other colors … and you will … ask your students if that reminds them of anything. Rainbows, and soap-bubbles, oily sheen are what comes to my mind.
  • What happens when marks “cross” each other? If you press hard when writing, where do you expect the marks to be thinnest?
Pickett_Image1

Figure 1

Here is what is happening. The “green” and “yellow” rays add up “constructively.” (See Figure 1.) That is, they are in constructive interference so you see this wavelength strongly reflected, even if this color were not present in the pigments of the oily marker layer.

The presence of this “rainbow” (see Figures 2 and 3) indicates that there is some interference going on, so the thickness of the marker layer has to be comparable to the wavelength of visible light.

Green light is in the neighborhood of 500 nanometers in wavelength, or 0.5 micrometer. A human red blood cell is approximately a disk of thickness 5 micron, and radius 15 micron, so the marks you use to teach physics are a factor of ten smaller than that cellular scale. When you teach physics, astrophysics, mathematics, history and poetry, you are using one of the great sub-micron teaching technologies of the twentieth century.

Dr. Galen T. Pickett is with the Department of Physics and Astronomy at CSU Long Beach and a member of CSTA.

Written by Guest Contributor

From time to time CSTA receives contributions from guest contributors. The opinions and views expressed by these contributors are not necessarily those of CSTA. By publishing these articles CSTA does not make any endorsements or statements of support of the author or their contribution, either explicit or implicit. All links to outside sources are subject to CSTA’s Disclaimer Policy: http://www.classroomscience.org/disclaimer.

Leave a Reply

LATEST POST

Participate in Chemistry Education Research Study, Earn $500-800 Dollars!

Posted: Tuesday, May 9th, 2017

WestEd, a non-profit educational research agency, has been funded by the US Department of Education to test a new molecular modeling kit, Happy Atoms. Happy Atoms is an interactive chemistry learning experience that consists of a set of physical atoms that connect magnetically to form molecules, and an app that uses image recognition to identify the molecules that you create with the set. WestEd is conducting a study around the effectiveness of using Happy Atoms in the classroom, and we are looking for high school chemistry teachers in California to participate.

As part of the study, teachers will be randomly assigned to either the treatment group (who uses Happy Atoms) or the control group (who uses Happy Atoms at a later date). Teachers in the treatment group will be asked to use the Happy Atoms set in their classrooms for 5 lessons over the course of the fall 2017 semester. Students will complete pre- and post-assessments and surveys around their chemistry content knowledge and beliefs about learning chemistry. WestEd will provide access to all teacher materials, teacher training, and student materials needed to participate.

Participating teachers will receive a stipend of $500-800. You can read more information about the study here: https://www.surveymonkey.com/r/HappyAtoms

Please contact Rosanne Luu at rluu@wested.org or 650.381.6432 if you are interested in participating in this opportunity, or if you have any questions!

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

2018 Science Instructional Materials Adoption Reviewer Application

Posted: Monday, May 8th, 2017

The California Department of Education and State Board of Education are now accepting applications for reviewers for the 2018 Science Instructional Materials Adoption. The application deadline is 3:00 pm, July 21, 2017. The application is comprehensive, so don’t wait until the last minute to apply.

On Tuesday, May 9, 2017, State Superintendent Tom Torlakson forwarded this recruitment letter to county and district superintendents and charter school administrators.

Review panel members will evaluate instructional materials for use in kindergarten through grade eight, inclusive, that are aligned with the California Next Generation Science Content Standards for California Public Schools (CA NGSS). Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

Lessons Learned from the NGSS Early Implementer Districts

Posted: Monday, May 8th, 2017

On March 31, 2017, Achieve released two documents examining some lessons learned from the California K-8 Early Implementation Initiative. The initiative began in August 2014 and was developed by the K-12 Alliance at WestEd, with close collaborative input on its design and objectives from the State Board of Education, the California Department of Education, and Achieve.

Eight (8) traditional school districts and two (2) charter management organizations were selected to participate in the initiative, becoming the first districts in California to implement the Next Generation Science Standards (NGSS). Those districts included Galt Joint Union Elementary, Kings Canyon Joint Unified, Lakeside Union, Oakland Unified, Palm Springs Unified, San Diego Unified, Tracy Joint Unified, Vista Unified, Aspire, and High Tech High.

To more closely examine some of the early successes and challenges experienced by the Early Implementer LEAs, Achieve interviewed nine of the ten participating districts and compiled that information into two resources, focusing primarily on professional learning and instructional materials. Learn More…

Written by California Science Teachers Association

California Science Teachers Association

CSTA represents science educators statewide—in every science discipline at every grade level, Kindergarten through University.

Using Online Simulations to Support the NGSS in Middle School Classrooms

Posted: Monday, May 8th, 2017

by Lesley Gates, Loren Nikkel, and Kambria Eastham

Middle school teachers in Kings Canyon Unified School District (KCUSD), a CA NGSS K-8 Early Implementation Initiative district, have been diligently working on transitioning to the Next Generation Science Standards (NGSS) integrated model for middle school. This year, the teachers focused on building their own knowledge of the Science and Engineering Practices (SEPs). They have been gathering and sharing ideas at monthly collaborative meetings as to how to make sure their students are not just learning about science but that they are actually doing science in their classrooms. Students should be planning and carrying out investigations to gather data for analysis in order to construct explanations. This is best done through hands-on lab experiments. Experimental work is such an important part of the learning of science and education research shows that students learn better and retain more when they are active through inquiry, investigation, and application. A Framework for K-12 Science Education (2011) notes, “…learning about science and engineering involves integration of the knowledge of scientific explanations (i.e., content knowledge) and the practices needed to engage in scientific inquiry and engineering design. Thus the framework seeks to illustrate how knowledge and practice must be intertwined in designing learning experiences in K-12 Science Education” (pg. 11).

Many middle school teachers in KCUSD are facing challenges as they begin implementing these student-driven, inquiry-based NGSS science experiences in their classrooms. First, many of the middle school classrooms at our K-8 school sites are not designed as science labs. Learn More…

Powered By DT Author Box

Written by NGSS Early Implementer

NGSS Early Implementer

In 2015 CSTA began to publish a series of articles written by teachers participating in the NGSS Early Implementation Initiative. This article was written by an educator(s) participating in the initiative. CSTA thanks them for their contributions and for sharing their experience with the science teaching community.

Celestial Highlights: May – July 2017

Posted: Monday, May 8th, 2017

May Through July 2017 with Web Resources for the Solar Eclipse of August 21, 2017

by Robert C. Victor. Twilight sky maps by Robert D. Miller. Graphs of planet rising and setting times by Jeffrey L. Hunt.

In spring and summer 2017, Jupiter is the most prominent “star” in the evening sky, and Venus, even brighter, rules the morning. By mid-June, Saturn rises at a convenient evening hour, allowing both giant planets to be viewed well in early evening until Jupiter sinks low in late September. The Moon is always a crescent in its monthly encounters with Venus, but is full whenever it appears near Jupiter or Saturn in the eastern evening sky opposite the Sun. (In 2017, Full Moon is near Jupiter in April, Saturn in June.) At intervals of 27-28 days thereafter, the Moon appears at a progressively earlier phase at each pairing with the outer planet until its final conjunction, with Moon a thin crescent, low in the west at dusk. You’ll see many beautiful events by just following the Moon’s wanderings at dusk and dawn in the three months leading up to the solar eclipse. Learn More…

Powered By DT Author Box

Written by Robert Victor

Robert Victor

Robert C. Victor was Staff Astronomer at Abrams Planetarium, Michigan State University. He is now retired and enjoys providing skywatching opportunities for school children in and around Palm Springs, CA. Robert is a member of CSTA.