The falling temperature of the photosphere with height is responsible for the effect known as limb darkening. The Sun is not equally bright all over the disc. When we observe the Sun towards the limbs, it appears to get darker. Light from the photosphere travels through an absorptive medium. Therefore, one can see only so far into the photosphere.…

Although it originates from the ancient Greeks, optics still arouses a lot of scientific interest, mainly due to the technological innovation associated with it. One of its most interesting applications is related to optical metrology and the characterization of materials through optical techniques. While some of these processes can be explained…

Sometimes it takes little to keep this physicist happy on an airplane. A window seat, where the plane's shadow is visible or has disappeared into the distance, provides the opportunity to observe a variety of phenomena associated with sunlight that is reflected, refracted or scattered back towards the Sun. The term "backscattering" is…

Pulsed field gradient nuclear magnetic resonance (NMR) is used to estimate the size of quantum dots (QDs) produced in a simple, fast, small-scale synthesis. This upper-division laboratory experiment teaches the basics of QD synthesis and pulsed field gradient NMR, a powerful technique for measuring diffusion coefficients in solution. The diffusion…

Demonstration interviews with 27 high school students (18-19 years old) were conducted in Zagreb, Croatia, using several standard experiments on interference and diffraction of light. Students were asked for their predictions, observations, and explanations of the experiments. In this process, many student difficulties were identified, both…

This article investigates the optics conceptions of 228 Thai high school students in grades 10-12 when they attempted to explain how an object can be seen both in general and in a completely dark room. To elicit students' conceptions precisely, their confidence in giving reasons for the final two diagnostic questions is also considered. The study…

In the last decades spectroscopy began to play an essential role in physics education research with the recognition that atomic spectra constitute a good occasion to study the concepts of quantum mechanics. Moreover, activities in which atomic spectra are studied in order to understand star structure and evolution have proved particularly engaging…

Plant leaves are green because they contain the green photosynthetic pigments, chlorophylls a and b. Popular science literature, and sometimes even textbooks, state that the greenness is caused by reflection of green light by chlorophyll. In the present study, we compared the reflectance spectra of green leaves to yellow or white leaves of the…

The field of geometrical optics features a broad knowledge base concerning conceptual learning difficulties and student conceptions. However, in contrast to other areas of physics, no widely used standard test instrument exists to assess middle school students' conceptual knowledge of geometrical optics. This is even more true for other areas of…

As intriguing optical phenomena that occur in nature, mirages are widely known and often mentioned in physics classes when introducing the basics of optics. In the atmosphere, a mirage occurs under the condition of vertical variations in air density, which are usually caused by a temperature gradient. The light rays are continuously refracted and…

Single slit diffraction and the thermal expansion of materials are common components of an undergraduate physics course, though these topics are often taught independently in both lectures and laboratory based courses. Higher levels of cognitive domains can be achieved by building on these established topics and combining them into a single…

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…

This paper proposes a simple method to design experiments for drawing the light paths at a lens to find its effective focal length and principal planes. In the designed experiments, long-exposure photography was used to record the light scattered using a moving sheet of paper, thus revealing the light path. According to the proposed experimental…

A popular introductory physics laboratory experiment is one focusing on Snell's law. This is straightforward to complete with lasers and prisms, but here we present an alternative version that guides the students through some of the major historical developments, recreating and analyzing significant experiments. The discovery of Snell's law has a…

In the vicinity of a critical point, the impact of a substance's chemical identity is superseded by universal critical behavior for a number of physical properties, such as visible light scattering. In this classroom demonstration, students observe a single-phase critical mixture of partially miscible isobutyric acid + water (IAW) as the…