Notes on the Reversal of the Sodium Line

The reversal of the sodium line may be demonstrated without the use of a slit or a spectroscope. An incandescent lamp having either a carbon or tungsten filament is placed immediately behind a good sodium flame and viewed from a distance of fifteen or twenty inches through a diffraction grating. The first- and second- order spectra, right and left, will both be in view and in the orange-yellow region of each will appear a sharp dark-line image of the filament of the lamp. This image constitutes the dark-line spectrum of the sodium vapor

Ball and Jet in a Vacuum

A report on an experimental and theoretical investigation of the equilibrium conditions for the case of a ball balanced on a jet of water

A Simple Device for Demonstrating the Tempered Scale

The diatomic scale consisting of a succession of eight tones and containing three intervals known as \u27\u27major second intervals,” two known as \u27\u27minor second intervals\u27\u27 and two half-tones, is not adapted to musical instruments of fixed pitch\u27\u27 (e.g. the piano, harp, etc.) for the reason that it does not without a multiplicity of keys (strings) allow of transposition or change of keys

The Moulding Action of Surface Tension on a Free Sheet of Water

A smooth stream of water falling vertically is allowed to strike the center of a small circular plate placed horizontally. The water under these circumstances spreads laterally over the edge of the plate in a thin stream. Under the action of gravity and surface tension this thin bubble-like stream assumes various forms determined by the velocity of the stream impinging upon the plate and the dimensions of the various parts of the apparatus. The bubble may be made to assume a more or less nearly spherical form or, by joining a free water surface below, to shape itself into the form of a bell. The smooth unbroken forms assumed by this film-stream are very striking, affording a beautiful illustration of surface tension effects and give promise of a convenient means of studying certain surface tension phenomena

A New Form of Carbon Arc

A convenient form of carbon arc for experimental and other work may be constructed at small cost in the following manner. Two straight arc-carbons of suitable size are mounted vertically side by side and parallel and separated by two or three millimeters. These carbons are connected to a 110-volt circuit with a resistance of 5 to 10 ohms, more or less, in series. If now the gap between the upper ends of the carbons is momentarily bridged by another carbon rod, an arc will form and remain when the short-circuiting carbon rod is removed

Visible Phase Relations in an A.C. Circuit

By connecting low wattage neon lamps in parallel with the different portions of an alternating current circuit the phase differences in these parts may be made visible by the rise and fall of the glow in the corresponding lamps

A Parallel Carbon Arc for Direct Current

An arc between carbons of equal diameter placed parallel to each other and spaced a small distance apart operates automatically on alternating current and the carbons burn down equally. When supplied with direct current the positive carbon is consumed at a rate approximately twice as great as that of the negative. Therefore to operate the ordinary parallel carbon arc on direct current some provision must be made to move the positive carbon forward, or a larger carbon must be used on the positive side of the circuit

Photomograph

A photometer is arranged in such manner that the screen and the lamp tested are stationary, the standard lamp being adjusted in distance to effect a balance. If the standard is moved by means of a band running over a wheel conveniently near the screen this wheel will revolve through an angle proportional to the distance the standard is moved

Students’ Perceptions of Choice-based Assessment

The traditional teacher-centered approach to assessment places teachers in total control of what, how, and when students’ learning is assessed. Alternatively, choice-based assessment is a learner-centered approach to assessment that allows students to choose, to some extent, what, how, and/or when their learning is assessed. A case study was designed to expose undergraduate students to a choice-based assessment strategy and subsequently measure the extent to which they agreed, or disagreed, that the strategy influenced their level of engagement and satisfaction with their learning. Students voluntarily shared their perceptions over two survey cycles (n=22 in spring 2017 and n=36 in fall 2017) with an overall response rate of 84 percent. Results clearly demonstrate that most students expressed strong support for this choice-based assessment strategy; it enabled them focus on their strengths and interests, it influenced their level of engagement, it made them feel more responsible for their learning, and it made them feel empowered. However, choice was not motivating for all students; a few students expressed concerns over the potential for procrastination, a lack of experience with choice, and/or too many choices, which were more likely symptoms of the strategy’s design rather than choice-based assessment. Overall, this case study clearly demonstrated that students were highly receptive to having a choice in what, how, and when their learning is assessed, which provides further evidence of the untapped potential for choice-based assessment strategies to foster student engagement, improve student satisfaction, and empower students to actively participate in their learning