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The visualization of interference fringes produced by the superposition of two different laser beams requires complex and costly demonstrations. This paper describes an experimental setup which (with the exclusion of an inexpensive and easy-to-build pair of optical guides) uses conventional laboratory equipment to detect the presence of the fringes.

Newton's rings were described in his work called Optiks and appeared when a lens was put on a glass sheet in daylight. These rings can also be measured in fluorescent light, and undergo a change in brightness with the same rhythmic gap found when a mercury light is used. A full explanation of the appearance of the rings using fluorescent light would require more research, but it appears likely that phosphorescence has an important role to play and phosphorescence involves time in a way that fluorescence does not.

Newton's first published paper, A New Theory About Light and Color, is intelligible to readers with no background in the subject. Described are demonstrations and experiments to accompany the teaching of this material.

An additivity equality of probability theory is suggested to define (relative) noninterference. Interference is deviation from this additivity. It is shown that two-slit interference fits into this scheme. It is argued that the physical meaning of quantum interference is an observable deviation of quantum filtering from quantum occurrence of events. The expounded view should restore the essence of textbook treatment of interference in a precise and correct probability-theoretic framework. The approach is essentially a continuation of a critical argument presented by Ballentine.

Sophomore physics majors in waves and optics can utilize a phasor model to observe multiple-slit interference patterns. The mechanical phasor model allows students to experience its qualitative and quantitative application first hand. The phasor is a helpful visual aid to augment standard algebraic analysis.

Newton's rings are often used in the physics classroom to demonstrate interference patterns but are hard to see with the traditional apparatus. A modified apparatus generates large rings that are visible to the whole class using a Plexiglass sheet with one kilogram weights at the corners to bend the sheet into a slightly convex shape. Visible light's wavelength is clearly demonstrated while the shape of the rings can be modified by adjusting the weights.

The traditional way of observing Newton's ring is modified with the use of a visualizer and an LCD projector to make lessons run more smoothly and more interesting. This method can also be used to measure light wavelengths and to study Brownian motion in a smoke cell.

This paper reports on a study of student understanding of the wave nature of matter in the context of the pattern produced by the diffraction and interference of particles. Students in first-year, second-year, and third-year physics courses were asked to predict and explain how a single change in an experimental setup would affect the pattern produced when electrons or other particles are incident on a single slit, double slit, or crystal lattice. The errors made by students after standard instruction indicated the presence of similar conceptual and reasoning difficulties at all levels. Among the most serious was an inability to interpret diffraction and interference in terms of a basic wave model. Other errors revealed a lack of a functional understanding of the de Broglie wavelength. Students often treated it as a fixed property of a particle, not as a function of the momentum. An important goal of this investigation was to provide a research base for the design of instruction to help students develop and apply a basic wave model for matter. [C] 2000 American Association of Physics Teachers.

A simulation method for illustrating interference using wavy lines drawn on the edge strips of pin fed computer paper and graph paper is described. The author suggests physic teachers should stock up on continuous feed computer paper for this experiment before it disappears.

A modified potentiometer can allow for the computerization of interference and diffraction experiments in the physics laboratory without significant expense. The modifications are designed to work with the PASCO computer interfaces but a device to convert an inexpensive potentiometer into a position transducer should be easily constructed. The details of the potentiometer conversion and prices are included.

Coherent light in the two arms of a Michelson interferometer are made circularly polarized but with opposite rotations. When the two beams recombine, the light is linearly polarized but the direction of polarization changes depending on the phase between the two beams. When a linear polarizer is used on the output and rotated, the observed interference fringe pattern shifts. If the field of view contains circular fringes, the continuous rotation of the polarizer in one direction makes the circles continuously expand or contract.

Results from an investigation of student understanding of physical optics indicate that university students who have studied this topic at the introductory level and beyond often cannot account for the pattern produced on a screen when light is incident on a single or double slit. Many do not know whether to apply geometrical or physical optics to a given situation and may inappropriately combine elements of both. Some specific difficulties that were identified for single and double slits proved to be sufficiently serious to preclude students from acquiring even a qualitative understanding of the wave model for light. In addition, we found that students in advanced courses often had mistaken beliefs about photons, which they incorporated into their interpretation of the wave model for matter. A major objective of this investigation was to build a research base for the design of a curriculum to help students develop a functional understanding of introductory optics.

An optional method of demonstrating thin film interference fringes with a laser uses a microscope slide glass cover in place of the normal mica sheet. An 18-by-18-mm. square glass cover with a nominal thickness of 0.15 mm. is used. The technique provides unique reflection fringes while allowing demonstrators to project the transmission fringes on a secondary viewing screen angled to the primary screen.