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"Optics Experiments."
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Experiments with light and color
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.
Book
Polar-Coded Transmission over 7.8-km Terrestrial Free-Space Optical Links
Free-space optical (FSO) communications can offer high-capacity transmission owing to the properties of the laser beams. However, performance degradation caused by atmospheric turbulence is an urgent issue. Recently, the application of polar codes, which can provide capacity-achieving error-correcting performance with low computational cost for decoding, to FSO communications has been studied. However, long-distance and real-field experiments have not been conducted in these studies. To the best of our knowledge, this study is the first to present the experimental results of polar-coded transmission over 7.8-km FSO links. Using experimental data, we investigated the performance of polar codes over atmospheric channels, including their superiority to regular low-density parity-check codes. We expect that our results will offer a path toward the application of polar codes in high-speed optical communication networks including satellites.
Journal Article
A project guide to light and optics
Looks at the history of the study of light and optics and presents science experiments and projects that demonstrate these principles.
Book
Light absorption properties and absorption budget of Southeast Pacific waters
Absorption coefficients of phytoplankton, nonalgal particles (NAPs), and colored dissolved organic matter (CDOM), and their relative contributions to total light absorption, are essential variables for bio-optical and biogeochemical models. However, their actual variations in the open ocean remain poorly documented, particularly for clear waters because of the difficulty in measuring very low absorption coefficients. The Biogeochemistry and Optics South Pacific Experiment (BIOSOPE) cruise investigated a large range of oceanic regimes, from mesotrophic waters around the Marquesas Islands to hyperoligotrophic waters in the subtropical gyre and eutrophic waters in the upwelling area off Chile. The spectral absorption coefficients of phytoplankton and NAPs were determined using the filter technique, while the CDOM absorption coefficients were measured using a 2 m capillary waveguide. Over the whole transect, the absorption coefficients of both dissolved and particulate components covered approximately two orders of magnitude; in the gyre, they were among the lowest ever reported for open ocean waters. In the oligotrophic and mesotrophic waters, absorption coefficients of phytoplankton and NAPs were notably lower than those measured in other oceanic areas with similar chlorophyll contents, indicating some deviation from the standard chlorophyll-absorption relationships. The contribution of absorption by NAPs to total particulate absorption showed large vertical and horizontal variations. CDOM absorption coefficients covaried with algal biomass, albeit with a high scatter. The spectral slopes of both NAP and CDOM absorption revealed structured spatial variability in relation with the trophic conditions. The relative contributions of each component to total nonwater absorption were (at a given wavelength) weakly variable over the transect, at least within the euphotic layer.
Journal Article
The cave of shadows : explore light and use science to survive
This is an adventure story with a difference! Follow Jess, Ben, Amelie, and Zac as they use science to escape from terrifying danger, and try some exciting experiments for yourself. In The Cave of Shadows, the gang uses the science of light to explore a huge, spooky cave in search of a lost puppy. Will they find Poppy the puppy? And will they ever find a way out again? Use experiments to find the answers to these fascinating questions: How can you see around corners? Can you separate light into different colors? How can you make your own magnifying glass? -- From cover page [4].
Book
Smoothness of stimulus motion can affect vection strength
We examined the effect of the smoothness of motion on vection strength. The smoothness of stimulus motion was modulated by varying the number of frames comprising the movement. In this study, a horizontal grating translated through 360° of phase in 1 s divided into steps of 3, 4, 6, 12, 20, 30, or 60 frames. We hypothesized that smoother motion should induce stronger vection because the smoother stimulus is more natural and contains more motion energy. We examined this effect of frame number on vection for both downward (Experiment 1) and expanding (Experiment 2) optical flow. The results clearly showed that vection strength increased with increasing frame rate, however, the rates of increase in the vection strength with frame rate are not constant, but rapidly increase in the low frame-rate range and appear to asymptote in the high range. The strength estimates saturated at lower frame rates for expanding flow than for downward flow. This might be related to the fact that to process expanding flow it is necessary to integrate motion signals across the visual field. We conclude that the smoothness of the motion stimulus highly affects vection induction.
Journal Article
Reconstruction of regional mean sea level anomalies from tide gauges using neural networks
The 20th century regional and global sea level variations are estimated based on long‐term tide gauge records. For this the neural network technique is utilized that connects the coastal sea level with the regional and global mean via a nonlinear empirical relationship. Two major difficulties are overcome this way: the vertical movement of tide gauges over time and the problem of what weighting function to choose for each individual tide gauge record. Neural networks are also used to fill data gaps in the tide gauge records, which is a prerequisite for our analysis technique. A suite of different gap‐filling strategies is tested which provides information about stability and variance of the results. The global mean sea level for the period January 1900 to December 2006 is estimated to rise at a rate of 1.56 ± 0.25 mm/yr which is reasonably consistent with earlier estimates, but we do not find significant acceleration. The regional mean sea level of the single ocean basins show mixed long‐term behavior. While most of the basins show a sea level rise of varying strength there is an indication for a mean sea level fall in the southern Indian Ocean. Also for the the tropical Indian and the South Atlantic no significant trend can be detected. Nevertheless, the South Atlantic as well as the tropical Atlantic are the only basins that show significant acceleration. On shorter timescales, but longer than the annual cycle, the basins sea level are dominated by oscillations with periods of about 50–75 years and of about 25 years. Consequently, we find high (lagged) correlations between the single basins.
Journal Article
Explore light and optics!
Imagine a world without light. What would it be like? Dark, cold, and lifeless! In this book, readers find out why light is so important to our world.
Book
Distribution of normalized water-leaving radiances at UV and visible wave bands in relation with chlorophyll a and colored detrital matter content in the southeast Pacific
In‐water radiometric measurements were performed in the southeast Pacific (8°S–35°S, 141°W–72°W) from October to December 2004 during the Biogeochemistry and Optics South Pacific Experiment cruise. Normalized water‐leaving radiances (nLw(λ)) were determined at eight wave bands within the ultraviolet (UV) (305, 325, 340, and 380 nm) and visible (412, 443, 490, and 565 nm) spectral domains. The highest nLw(λ) (μW cm−2 sr−1) were recorded in the hyperoligotrophic waters of the South Pacific Gyre, with values increasing with wavelength from 305 (nLw = 0.64) to 380 nm (nLw = 3.18) in the UV range and decreasing from 412 (nLw = 4.46) to 565 nm (nLw = 0.23) in the visible region. The intense nLw(λ) observed in the violet‐blue domains were attributed to very low absorptions of colored detrital matter (CDM), likely related to a strong photobleaching of colored dissolved organic matter in the surface waters. We evaluated the relationships between the UV, violet, or blue/green wave band ratios of nLw(λ) and surface total chlorophyll a (TChl a) concentration and CDM absorption (aCDM(λ)). For TChl a, the best correlation was found with the blue/green ratio at 443 nm: TChl a (mg m−3) = 2.37[nLw(443)/nLw(565)]−1.51 (r2 = 0.86 and RMS error (RMSE) = 23%). By contrast, for aCDM(λ), the best correlation was observed when using the UV/green ratio at 325 nm: aCDM(325) (m−1) = 0.16[nLw(325)/nLw(565)]−0.69 (r2 = 0.82 and RMSE = 16%). These results show the potential role of nLw(λ) at UV wave bands for the assessment, through empirical algorithms, of colored detrital matter in the surface oceanic waters.
Journal Article