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Presents simple experiments, with step-by-step, illustrated instructions, for studying the science of light, including how rainbows are made and how light can change directions.

Actin filament’s polyelectrolyte and hydrodynamic properties, their interactions with the biological environment, and external force fields play an essential role in their biological activities in eukaryotic cellular processes. In this article, we introduce a unique approach that combines dynamics and electrophoresis light-scattering experiments, an extended semiflexible worm-like chain model, and an asymmetric polymer length distribution theory to characterize the polyelectrolyte and hydrodynamic properties of actin filaments in aqueous electrolyte solutions. A fitting approach was used to optimize the theories and filament models for hydrodynamic conditions. We used the same sample and experimental conditions and considered several g-actin and polymerization buffers to elucidate the impact of their chemical composition, reducing agents, pH values, and ionic strengths on the filament translational diffusion coefficient, electrophoretic mobility, structure factor, asymmetric length distribution, effective filament diameter, electric charge, zeta potential, and semiflexibility. Compared to those values obtained from molecular structure models, our results revealed a lower value of the effective G-actin charge and a more significant value of the effective filament diameter due to the formation of the double layer of the electrolyte surrounding the filaments. Contrary to the data usually reported from electron micrographs, the lower values of our results for the persistence length and average contour filament length agree with the significant difference in the association rates at the filament ends that shift to sub-micro lengths, which is the maximum of the length distribution.

This introduction to the power and versatility of light includes experiments in white light, the color spectrum, and how light changes direction when it passes from one medium to another.

Demonstration of an optomechanical system that works as a quantum interface between light and micro-mechanical motion. Nanomechanical oscillators coupled to optic cavities The possibility of controlling the quantum states of micro- and nanomechanical oscillators has been of great interest in recent years. Although various mechanical resonators have been cooled to their quantum ground state, there are few reports of experiments in which this quantum regime is further explored and used, for example, to exchange quantum information. Previously, quantum coupling between mechanical degrees of freedom and microwave radiation has been shown. Now, Verhagen et al . demonstrate an optomechanical system, cooled by radiation pressure, that works as a quantum interface between a mechanical oscillator and optical photons, offering the advantage that standard optical fibres can be used to extract the quantum information. Optical laser fields have been widely used to achieve quantum control over the motional and internal degrees of freedom of atoms and ions 1 , 2 , molecules and atomic gases. A route to controlling the quantum states of macroscopic mechanical oscillators in a similar fashion is to exploit the parametric coupling between optical and mechanical degrees of freedom through radiation pressure in suitably engineered optical cavities 3 , 4 , 5 , 6 . If the optomechanical coupling is ‘quantum coherent’—that is, if the coherent coupling rate exceeds both the optical and the mechanical decoherence rate—quantum states are transferred from the optical field to the mechanical oscillator and vice versa. This transfer allows control of the mechanical oscillator state using the wide range of available quantum optical techniques. So far, however, quantum-coherent coupling of micromechanical oscillators has only been achieved using microwave fields at millikelvin temperatures 7 , 8 . Optical experiments have not attained this regime owing to the large mechanical decoherence rates 9 and the difficulty of overcoming optical dissipation 10 . Here we achieve quantum-coherent coupling between optical photons and a micromechanical oscillator. Simultaneously, coupling to the cold photon bath cools the mechanical oscillator to an average occupancy of 1.7 ± 0.1 motional quanta. Excitation with weak classical light pulses reveals the exchange of energy between the optical light field and the micromechanical oscillator in the time domain at the level of less than one quantum on average. This optomechanical system establishes an efficient quantum interface between mechanical oscillators and optical photons, which can provide decoherence-free transport of quantum states through optical fibres. Our results offer a route towards the use of mechanical oscillators as quantum transducers or in microwave-to-optical quantum links 11 , 12 , 13 , 14 , 15 .

Disappearing coins, balloon megaphones, CD rainbows... the science of light and sound sometimes seems like magic! Readers will learn the amazing facts behind these phenomena that are more fascinating than fiction. Simple language explains the properties of light and sound, while hands-on activities give readers tangible examples to help them retain crucial science information.

All optical detectors to date annihilate photons upon detection, thus excluding repeated measurements. Here, we demonstrate a robust photon detection scheme that does not rely on absorption. Instead, an incoming photon is reflected from an optical resonator containing a single atom prepared in a superposition of two states. The reflection toggles the superposition phase, which is then measured to trace the photon. Characterizing the device with faint laser pulses, a single-photon detection efficiency of 74% and a survival probability of 66% are achieved. The efficiency can be further increased by observing the photon repeatedly. The large single-photon nonlinearity of the experiment should enable the development of photonic quantum gates and the preparation of exotic quantum states of light.

\"Budding scientists will love learning about the properties of light by planning and carrying out investigations that explore how the energy form can be reflected, manipulated, and refracted.\"-- Provided by publisher.

Everyone knows that you can read a galloping horse in a still image as galloping. This paper asks how it is that we perceive motion in pictures. It considers perception of real motion in point-light experiments and the perception of motion in stills via the work of various psychologists, in the course of which it raises theoretical questions about the nature of visual perception. It then offers a detailed examination of knowledge regarding neural substrates for both real and depicted motion perception. Finally, it combines psychological and neurophysiological perspectives with phenomenologically-oriented observation of pictures, discussing both frontoparallel motion and motion in depth (in particular the phenomenon of “looming”) in terms of two kinds of depictions, the “narrative” and the “performative”. Examples are drawn from all kinds of pictures, but focus is on world rock art, whose time depth is especially amenable to the universalist approach adopted by the paper.

Looks at the history of the study of light and optics and presents science experiments and projects that demonstrate these principles.

Cool quantum science In recent years micromechanical devices have been developed that can strongly couple to light, by integrating them within optical cavities. A main goal has been to cool the devices optomechanically, freezing out all thermal vibrations, so that the object's motion eventually becomes limited by quantum mechanical fluctuations. This would make it possible to study a new range of quantum behaviour of mechanical objects. Thompson et al . report an improved design of such a system, involving a movable membrane sandwiched between two rigid high-quality mirrors. In previous designs one of the mirrors had to double-up as a microresonator. The new device achieves substantial cooling, from room temperature to 6.8 mK. It should eventually be possible to reach the quantum-limited ground state with this system. A report on an improved design of an optomechanical system in which a movable membrane is placed between two rigid high-quality mirrors, as opposed to previous designs where one of the mirrors has a double function as the microresonator; it's claimed that it is feasible to reach the quantum-limited ground state with this new design. Macroscopic mechanical objects and electromagnetic degrees of freedom can couple to each other through radiation pressure. Optomechanical systems in which this coupling is sufficiently strong are predicted to show quantum effects and are a topic of considerable interest. Devices in this regime would offer new types of control over the quantum state of both light and matter 1 , 2 , 3 , 4 , and would provide a new arena in which to explore the boundary between quantum and classical physics 5 , 6 , 7 . Experiments so far have achieved sufficient optomechanical coupling to laser-cool mechanical devices 8 , 9 , 10 , 11 , 12 , but have not yet reached the quantum regime. The outstanding technical challenge in this field is integrating sensitive micromechanical elements (which must be small, light and flexible) into high-finesse cavities (which are typically rigid and massive) without compromising the mechanical or optical properties of either. A second, and more fundamental, challenge is to read out the mechanical element’s energy eigenstate. Displacement measurements (no matter how sensitive) cannot determine an oscillator’s energy eigenstate 13 , and measurements coupling to quantities other than displacement 14 , 15 , 16 have been difficult to realize in practice. Here we present an optomechanical system that has the potential to resolve both of these challenges. We demonstrate a cavity which is detuned by the motion of a 50-nm-thick dielectric membrane placed between two macroscopic, rigid, high-finesse mirrors. This approach segregates optical and mechanical functionality to physically distinct structures and avoids compromising either. It also allows for direct measurement of the square of the membrane’s displacement, and thus in principle the membrane’s energy eigenstate. We estimate that it should be practical to use this scheme to observe quantum jumps of a mechanical system, an important goal in the field of quantum measurement.