Optics

If you haven’t the infinite ammo of the late Hunter S. Thompson or the lightning-fast trigger finger (and impressive spray radius) of a recent Vice President, it actually takes considerable skill to shoot a fish in a barrel (exact difficulty proportional to size of barrel and fish depth and inversely proportional to size of fish). Some of this trickiness is due to refraction, or the change in speed and thus direction of light waves as they move from air to water.

Wait a minute!? Isn’t the speed of light constant?

Yes. But only in a vacuum.
The next time an overnight snow begins to fall, take two bricks and place them side by side a few inches apart in your yard.  In the morning, the bricks will be covered with snow and barely discernible. The snowflakes will have filled every vacant space between and around the bricks.

What you will see, says Ivan Biaggio, an associate professor of physics at Lehigh University, resembles a phenomenon that, when it occurs at the smallest of scales on an integrated optical circuit, could hasten the day when the Internet works at superfast speeds.
Scientists are harnessing the cosmos as a scientific “instrument” in their quest to determine the makeup of the universe.   Evalyn Gates calls from the University of Chicago calls it “Einstein’s telescope” but she actually means the phenomenon of gravitational lensing, which acts as a sort of natural telescope.

In general relativity, mass can warp space and create gravitational fields that bend light - confirmed in  by Arthur Eddington during a solar eclipse, when he saw that the light from stars that passed close to the sun was slightly bent, making them appear out of position.
Demands on telescope technology are rapidly increasing as astronomers look at fainter and fainter objects in the night sky. The large amount of light collection area required to view very dim objects poses a number of significant engineering problems to future telescope designers. To collect short-wavelength radio waves, for instance, an antenna miles across would be required. This has led engineers to construct multiple small telescopes whose signals can be integrated, providing the necessary level of detail.
Sliced light is how we communicate now. Millions of phone calls and cable television shows per second are dispatched through fibers in the form of digital zeros and ones formed by chopping laser pulses into bits. This slicing and dicing is generally done with an electro-optic modulator, a device for allowing an electric signal to switch a laser beam on and off at high speeds (the equivalent of putting your hand in front of a flashlight). Reading that fast data stream with a compact and reliable receiver is another matter. A new error-free speed-reading record using a compact ultra-fast component—640 Gbits/second (Gbps, or billion bits per second)—has now been established by a collaboration of scientists from Denmark and Australia.
Uniform and mottle patterns are what most people recognize as camouflage and those patterns function by resembling the background.    True background matching is not simple, though, and Roger T. Hanlon and colleagues say they are making one of the first efforts to quantify camouflage body patterns.

Although they have begun to compare camouflage tactics in many animals — large primates, amphibians, reptiles, fishes, insects — they are currently focusing on the cephalopods, which include squid, octopus, and cuttlefish. Remarkably, these soft-bellied mollusks are able to dynamically produce all three classes of camouflage body patterns (termed uniform, mottled, and disruptive). 
'Cloaking' devices bend electromagnetic waves, such as light, in such a way that it appears as if the cloaked object is not there. In the latest laboratory experiments by Duke researchers, a beam of microwaves aimed through the cloaking device at a "bump" on a flat mirror surface bounced off the surface at the same angle as if the bump were not present. Additionally, the device prevented the formation of scattered beams that would normally be expected from such a perturbation.

The underlying cloaking phenomenon is similar to the mirages seen ahead at a distance on a road on a hot day.
In 1609, 400 years ago, Galileo revolutionized humankind's understanding of our position in the Universe when he used a telescope for the first time to study the heavens and sketched radical new views of the moon and also discovering the satellites orbiting Jupiter.

To celebrate the International Year of Astronomy (IYA), which marks the anniversary of Galileo's discoveries, a group of astronomers and curators from the Arcetri Observatory and the Institute and Museum of the History of Science, both in Florence, Italy, are recreating the kind of telescope and conditions that led to Galileo's world-changing observations, reports January's Physics World.
Using a beam of light shunted through a tiny silicon channel, researchers have created a nanoscale trap that can stop free floating DNA molecules and nanoparticles in their tracks. By holding the nanoscale material steady while the fluid around it flows freely, the trap may allow researchers to boost the accuracy of biological sensors and create a range of new 'lab on a chip' diagnostic tools.

Light has been used to manipulate cells and even nanoscale objects before, but the new technique allows researchers to manipulate the particles more precisely and over longer distances.
Deriving plentiful electricity from sunlight at a modest cost is a challenge with immense implications for energy, technology, and climate policy. A paper in a special energy issue of Optics Express, describes a relatively new approach to solar cells: lacing them with nanoscopic metal particles. As the authors describe in the article, this approach has the potential to greatly improve the ability of solar cells to harvest light efficiently.