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Laser light can create its own shadow scientists say
>> YOUR LINK HERE: ___ http://youtube.com/watch?v=rHnGn7lushc
/ @golahura Laser light can create its own shadow, scientists say. • Scientists say that the idea of shadows needs to be reconsidered. • Shadows are created when an object blocks the passage of incoming light. It was thought that light beams would not create shadows because photons have no mass. • Normally, two light beams that intersect pass through each other. However, a new study has shown that a different scenario can occur. • The research team, which studied how light beams interact under normal conditions, used three-dimensional modeling software to create simple diagrams for the experiments. • The physicists found it funny at first when they saw that the software showed the light beam as a solid object. But then they decided to dig deeper into this unexpected situation. • They conducted an experiment with ruby, a material often used to study the behavior of light in nonlinear environments. • The researchers projected blue laser light onto one side of a cube-shaped ruby. The blue light passed through the object and gave a cold glow to the screen opposite. • The thinner beam of the green laser was then projected at a right angle to the other. • Where the thin line of green light fell on the molecules of the ruby, electrons began to rise and fall. This prevented the slightly shorter wavelength blue light from passing through the normally translucent material. • The green laser beam then acted like an object, creating a dark line in the blue light that fell on the screen on the other side of the ruby. • According to the paper published yesterday (Nov. 14) in the peer-reviewed journal Optica, the line met the criteria for a shadow: It was visible to the naked eye, matched the contours of the screen it fell on, and moved with the green laser beam when the laser source was moved. • This discovery opens up new possibilities for using light in ways we had not previously considered, expanding our understanding of light-matter interactions, says lead author Raphael Abrahao. • Our understanding of shadows has evolved hand in hand with our understanding of light and optics. This new finding could be useful in a variety of applications, including optical switching, devices in which light controls the presence of other light, or technologies that require precise control of light transmission, such as very powerful lasers. • The green laser actually excites some of the crystal’s electrons, which then decay and absorb the blue light, creating a shadow. The team acknowledges this in the paper, writing: • The laser shadow effect requires the ruby to provide a barrier, which raises an interesting question: Is it the photons in the laser acting as an object that block the illuminating light, or is it the atoms in the ruby? • Still, the shadow that is cast is real, and Abrahao thinks the new study could use some updates. “It was thought impossible for laser light to create shadows because light usually passes through other light without interacting,” the physicist says.
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