The refractive index is a number that governs how light changes its direction of propagation as it enters one material medium from another. This phenomenon is known as refraction and the angles of incidence and refraction of light, referred to the normal to the interface of the two media at the point of incidence, are related by Snell's law. The…

Possibly the greatest irony of physics education is the difficulty of demonstrating optics in a visible way. The two most common solutions to this conundrum are to either use "all-inclusive" optical apparatuses, like a large-format camera, or to rely on classic ray-tracing diagrams. While the former looks elegant while demonstrating the…

The typical sound of George Lucas' laser blaster in the "Star Wars" series is well known. What does a laser blaster in "Star Wars" sound like, and why? Here we show a simple way to produce this sound by using low-cost lab material, like a spring or a Slinky. Building on the work of Crawford, who analyzed the sound of a Slinky…

The laser pointer has been widely used to demonstrate some simple optics phenomena, like reflection, refraction, total reflection, and diffraction. However, the rays of laser light cannot be seen in the air because the scattered light is too weak. Many physics teachers use milk or smoke to visualize rays of laser light in physics labs, but it is…

A diffraction grating is a plane surface having a large number of closely spaced slits running in parallel. When light of appropriate wavelength is incident on a diffraction grating it functions as a spectrometer, able to separate the light into its spectral components. Physical examples of interest for diffraction in the real world are…

This article describes a simple way to introduce nanomaterials using the presence of carbon nanodots (CNDs) in widely available food. Budweiser® beer and Coca-Cola®, commercial foods that are commonly accessible, were utilized to demonstrate the optical property of nanoparticles. Specifically, green and violet laser pointers were employed for the…

This study aims to measure Brewster's angle of glass and acrylic brick with an easy-to-obtain mobile application (app) by changing the tungsten light source to a red laser. The popularization of the smartphone has inspired many to use its various built-in sensors to carry out general physics experiments. Many others have adopted both a laser and a…

The author has acquired a yellow laser with the specific wavelength of 589 nm. Because this is the first time such a laser has been discussed in this journal, I feel it is appropriate to provide a discussion of its function and capabilities. Normal laser safety should be employed, such as not pointing it into eyes or at people, and using eye…

Fluorescence spectra excited by laser pointers have been the subject of several papers in "TPT". These papers all describe a fluorescence phenomenon in which the reflected laser light undergoes a change in color: this color change results from the combination of some partially reflected laser light and additional colors generated by…

A compact disc (CD) can be used as a diffraction grating, even though its track consists of a series of pits, not a continuous groove. Previous authors described how to measure the track spacing on a CD using an incident laser beam normal to the surface or one at an oblique angle. In both cases, the diffraction pattern was projected on a screen…

Suppose a red laser beam (of wavelength ? equal to 0.660 µm) is expanded using an optical telescope into a collimated, approximately plane wave that is 5.68 mm in diameter. Pass that beam through a tall rectangular slit whose width "a" is gradually reduced from 3.30 to 0.100 mm. Look at its image on a screen located at a distance…

The Kaleidophone, invented by Charles Wheatstone (1802-1875) in 1827, is a delightful mixture of physics and art. A typical example of the device, dating from the latter part of the 19th century, is shown in Fig. 1. The upright rods, which are approximately 25 cm in length, are of variously circular, oval, square, and rectangular cross section,…

Understanding the inverse square law, how for example the intensity of light or sound varies with distance, presents conceptual and mathematical challenges. Students know intuitively that intensity decreases with distance. A light source appears dimmer and sound gets fainter as the distance from the source increases. The difficulty is in…

We present a simple method to determine the refractive indices of transparent media using a laser distance meter. Indices of refraction have been obtained by measuring the speed of light in materials. Some speed of light techniques use time-of-flight measurements in which pulses are emitted by lasers and the time interval is measured for the pulse…

For decades now, the laser has been used as a handy device for performing ray traces in geometrical optics demonstrations and laboratories. For many ray- trace applications, I have found the laser level 3 to be even more visually compelling and easy for student use than the laser pointer.