Volume 47, Issue 5, May 2009
- letters to the editor
- aapt awards
- figuring physics
- united states association for young physicists tournaments (usaypt)
- apparatus for teaching physics
- trick of the trade
- fermi questions
- for the new teacher
- physics challenge for teachers and students
- youtube physics
- book reviews
Index of content:
47(2009); http://dx.doi.org/10.1119/1.3116834View Description Hide Description
When a college instructor goes out of town and must miss a lecture, the standard options are to cancel the class meeting or to enlist a colleague to fill in. In the former case a teaching opportunity is lost; in the latter the substitute may not lead the class in the same way as the instructor. Some students routinely skip lectures by a guest instructor, in the belief that the material in the substitute lecture will not be covered on the exam. There are other makeup options such as a directed study assignment. For instance, a missed class is sometimes a good opportunity to require students to investigate web-based simulations such as Physlets® that illustrate the class topics. These are most effective if the students are given a clear structure and if there are questions that the students must answer from their investigations with the Physlets. But many students are more comfortable with the audio and visual communication that occurs in the classroom. Web 2.0 technology, e.g., YouTube (http://www.youtube.com), makes it convenient for faculty to upload videos of lectures and demonstrations that can be used for makeup classes. College students already use YouTube for entertainment, and the YouTube format is simple to view on any web-connected computer. Although some universities have highly developed media delivery systems, YouTube is extremely convenient and accessible by anyone. This paper discusses how a YouTube makeup class can be efficiently produced and structured to be an effective learning experience.1
47(2009); http://dx.doi.org/10.1119/1.3116835View Description Hide Description
To investigate the frontiers of particle physics,physicists and engineers are building detectors and making measurements in unusual settings from outer space to far-flung regions of the Earth. In the past several decades, laboratories have been set up deep underground in working mines or mountain tunnels to look at subatomic particles from our Sun and to search for the strange dark matter particles needed to explain the evolution of galaxies. This paper describes important current developments in astroparticle physics, the SNOLAB underground laboratory in Sudbury, Canada, and several of the experiments that are being developed in that facility.
47(2009); http://dx.doi.org/10.1119/1.3116836View Description Hide Description
Early in my career someone else reported that the best indicator of success in calculus-based physics (CBP) at our school was whether students had taken mathematics in a certain region of New Brunswick. I sat down with a very longtime mathematics teacher and asked him what he thought students should know in mathematics after high school to succeed in college. He quickly gave me five areas that every student should know and pointedly indicated that it was best to give them the questions and watch how they attacked the problems. A solution was not even important; all one had to note was the immediate steps that the student took.
47(2009); http://dx.doi.org/10.1119/1.3116837View Description Hide Description
In response to student requests, and to help celebrate the graduation of our physics majors, we have designed a graduation stole uniquely befitting physics. The design incorporates the four visible spectral lines of hydrogen—the Balmer series. Since the 2002 debut of the design, all our graduates have proudly worn their physics graduation stoles at commencement. We hope the idea of a unique physics graduation stole, and the specific design of this particular one, will help spread the celebration of physics to other institutions as well.
47(2009); http://dx.doi.org/10.1119/1.3116838View Description Hide Description
In problems dealing with the Earth's gravity, students are frequently bewildered by the fact that the two common expressions for potential energy, mgh and −Gm e m/r, differ in sign and differ considerably in form. Some textbooks demonstrate that the more familiar first expression is a special case of the more general second equation providing that an object is near to the Earth's surface.1–2 In this paper I derive an equation that resembles the familiar U = mgh but that applies to an object of mass m at any height h above the Earth's surface.
47(2009); http://dx.doi.org/10.1119/1.3116839View Description Hide Description
Rayleigh's criterion states that a pair of point sources are barely resolved by an optical instrument when the central maximum of the diffraction pattern due to one source coincides with the first minimum of the pattern of the other source. As derived in standard introductory physicstextbooks,1 the first minimum for a rectangular slit of width a is located at angular position for light of wavelength λ. If the angular separation of the two sources is small, we can use the small-angle approximation sin θ ≈ θ to conclude that the resolution is for a rectangular aperture. On the other hand, for a circular aperture of diameter D, the limiting angle is shown in optics texts2 to be The derivation of the numerical prefactor of 1.22 involves finding the zero of a Bessel function and is beyond the reach of introductory physics students. Consequently, elementary texts simply pull that prefactor out of thin air. The purpose of the present paper is to briefly explain why we expect a prefactor larger than unity and to make simple estimates of its value, using only algebra.
47(2009); http://dx.doi.org/10.1119/1.3116840View Description Hide Description
Cross-curricular secondary instructional strategies exist in many different forms and can be applied to any two or more curricular disciplines. Most importantly, these strategies have been proven to be effective in improving learning and comprehension of important concepts across all curricular fields involved in the activity.1–7 There is no instructional strategy as applicable and as important to secondary students in all classes, particularly English Language Learners (ELLs),8,9 as the implementation of writing into a curricular discipline.
47(2009); http://dx.doi.org/10.1119/1.3116841View Description Hide Description
This note describes how white light interference fringes can be seen by observing the Moon through a double-glazed window. White light interferometric fringes are normally observed only in a well-aligned interferometer whose optical path difference is less than the coherence length of the light source, which is approximately one micrometer for white light. Obtaining such fringes in a Michelson interferometer is not a trivial task.1 The interferometer is typically illuminated with a monochromatic source and the path length difference adjusted with a wedge angle between the interferometermirrors so that five or six vertical fringes are visible, indicating nearly equal paths. Then the mirrors are adjusted until the fringes are almost perfectly straight. Finally we use a white light source and carefully scan through the approximately equal path range until five or six white light fringes are seen to sweep rapidly by.
47(2009); http://dx.doi.org/10.1119/1.3116842View Description Hide Description
This paper describes my attempts to look deeper into the so-called “shoot for your grade” labs, started in the '90s, when I began applying my teaching experience in Russia to introductory physics labs at the College of Charleston and other higher education institutions in South Carolina. The term “shoot for your grade” became popular among teachers of a projectile motion lab where students are graded based on their ability to predict the range of the projectile. I describe here several additional laboratory exercises in which students are required to predict results of the experiment. I also discuss an essential element of these exercises which I call “recurrent study.”