An extraordinary tabletop speed of light apparatus

Pegna, G.

doi:10.1119/1.4985728

Cited by 6 publications

(2 citation statements)

References 21 publications

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“…At the advanced level courses, the students can examine the time variation of the brightness of the laser beam (using an oscilloscope) and find out that it periodically switches on and off at frequency of the order of 10 MHz. At this point students are ready to learn about the modulation-based phase shift method for measuring distances and compare and contrast it with the pulse time-of-flight method (see for example [30]) 5 .…”

Section: Lmd If Studentsmentioning

confidence: 99%

Framework for using modern devices in introductory physics courses

Planinšič

Etkina

2019

Eur. J. Phys.

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In this paper we introduce a practical framework that guides teachers on how to integrate modern devices (MD) into an existing physics course without adding new topics. The framework has three components: using the device as a black box, using the device to learn the physics behind its operation and using the device to learn new physics. We used two devices (a laser distance meter and an LED) to illustrate how to apply this framework in instruction. We provide examples of learning activities and ideas that students bring in when they engage in these activities. We hope that the framework will encourage and help teachers to systematically use MD in their courses in suggested ways.

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Section: Lmd If Studentsmentioning

confidence: 99%

Framework for using modern devices in introductory physics courses

Planinšič

Etkina

2019

Eur. J. Phys.

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“…Phase shift measurements include amplitude-modulated light beams produced by means of Kerr cell [9], modulated LEDs [10,11], laser pointers [12,13], or modulated laser [14,15]. Recently, Pegna [16] has published an apparatus that modulates a collimated red laser at a frequency of 433.92 MHz, making possible a speed of light demonstration within a sub-metre measuring base.…”

Section: Introductionmentioning

confidence: 99%

Speed of light demonstration using Doppler beat

Bernal

Bilbao

2018

Eur. J. Phys.

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From an apparatus previously designed for measuring the Doppler shift using a rotating mirror, an improved, versatile version was developed for speed-of-light demonstrations in a classroom or a teaching laboratory. By adding a second detector and adequate beam-splitter and mirrors three different configurations are easily assembled. One configuration is used for time-of-flight measurements between a near and a far detector, allowing to measure the speed of light provided that the path length between detectors is known. Another variation is the interferometric method obtained by superposing the far and near signals, in such a way that a minimum of the combined signal is obtained when the time delay makes the signals arrive out of phase by π radians. Finally, the standard Doppler configuration allows the measurement of the frequency beat as a function of the rotation frequency. The main advantages of the apparatus are: a) the experimental setup is simple and completely accessible to undergraduate students, b) the light is visible, students can see the rays, which, with the use of appropriate screens, can be blocked at any point along their paths, c) the experiment can take place entirely within the teaching laboratory or demonstration room (using the interferometric method, the shortest distance to the far mirror was as small as 0.5 m), d) different configurations can be built, including some economical setups within the budget of teaching laboratories.

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Relativistic jets: An astrophysical laboratory for the Doppler effect

Zakamska

2018

American Journal of Physics

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Special Relativity is one of the most abstract courses in the standard curriculum for physics majors, and therefore practical applications or laboratory exercises are particularly valuable for providing real-world experiences with this subject. This course poses a challenge for lab development because relativistic effects manifest themselves only at speeds close to the speed of light. The laboratory described in this paper constitutes a low-cost, low-barrier exercise suitable for students whose only background is the standard mechanics-plus-electromagnetism sequence. The activity uses research-quality astronomical data on SS433—a fascinating Galactic X-ray binary consisting of a compact object (a neutron star or a black hole) and a normal star. A pair of moderately relativistic jets moving with v∼0.3c in opposite directions emanate from the vicinity of the compact object and are clearly detected in optical and radio observations. Following step-by-step instructions, students develop a full kinematic model of a complex real-world source, use the model to fit the observational data, obtain best-fit parameters, and understand the limitations of the model. The observations are in exquisite agreement with the Doppler effect equations of Special Relativity. The complete lab manual, the dataset and the solutions are available in online supplemental materials; this paper presents the scientific and pedagogical background for the exercise.

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An extraordinary tabletop speed of light apparatus

Cited by 6 publications

References 21 publications

Framework for using modern devices in introductory physics courses

Framework for using modern devices in introductory physics courses

Speed of light demonstration using Doppler beat

Relativistic jets: An astrophysical laboratory for the Doppler effect

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