| Dec 04, 2020 |
An optical curveball (w/video)(Nanowerk News) Have you ever been amazed by a curveball goal scored by Diego Maradona, Lionel Messi or Christiano Ronaldo? Then you have – possibly without knowing it – been exposed to the Magnus effect: the fact that spinning objects tend to move along curved paths. |
| In a new publication that appeared in Physical Review Letters ("Off-Axis Dipole Forces in Optical Tweezers by an Optical Analog of the Magnus Effect"), Robert Spreeuw shows that the same effect occurs to atoms moving through light – and that this effect has practical consequences. |
| Even though many people may have never heard the name, the Magnus effect is well known in our daily lives. On YouTube, videos show football playersscoring incredible-looking goalsusing the effect, and there exists a 45-million-view video that shows what happens when youthrow a spinning basketball off a dam. |
| All of these videos show the same basic effect: when a spinning object moves through the air, a pressure difference caused by the spinning causes the path of the object to curve. |
| Physicist Robert Spreeuw (UvA Institute of Physics) has now shown that the same effect occurs also on a much smaller scale. Replace the football by an atom, or any other microscopic object that has a so-called ‘dipole moment’, an asymmetry in the way that its electric charge is distributed. |
| Don’t let this atom move through the air, like the ball did – air itself consists of atoms, so the moving atom would simply bounce back and forth – but let it move through a beam of laser light instead. The light will exert a pressure on the atom just like the air did on the football, and voilá: the atom experiences a sideways force. |
| This in turn has an effect on the light: just like the stream of air around the football is affected by its spin, the laser beam also measurably bends around the atom. |
| The result is not just useful for scoring goals in the world’s smallest miniature football game. The optical Magnus effect also affects optical tweezers: devices that use light to delicately handle and move individual atoms. |
| Such tweezers, for which a Nobel Prize was awarded in 2018, are a much-used tool – for example in the development of quantum computers. Atoms in optical tweezers also experience a sideways force caused by the optical Magnus effect, and therefore the new knowledge of this effect will help us handle these devices in an even more precise manner. |
| Source: University of Amsterdam | |
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