First Ever Photograph of Light Behaving as Both a Particle and a Wave
Scientists have long theorized that light acts as both a wave and a particle, but have never been able to directly observe it. Now, a new experiment by researchers at EPFL has shown light in all of its paradoxical glory, and captured a photograph of light behaving as both a particle and a wave.
Visible light exhibits a property predicted by quantum mechanics called wave-particle duality. Certain behaviors such as diffraction and interference seem to indicate that it's a wave, while others, such as reflection and polarization, are consistent with a stream of particles. Scientists were puzzled by this apparent contradiction, but ultimately discovered that light can be mathematically represented by a wave function or a stream of particles, depending on the situation. Or, in other words, it is in some sense both a wave and a particle, and in another sense neither a wave nor a particle.
Although we've known that light exhibits wave-particle duality for some time now, scientists have never been able to observe light behaving as both a particle and a wave simultaneously. But in this experiment, the researchers came up with the groundbreaking method of using electrons to image light, and the result was the first image of light as a particle and a wave:
[Credit: Fabrizio Carbone/EPFL]
In order to take this photograph, the researchers shot pulses of laser light at a metal nanowire, causing the charged particles in the wire to vibrate. Then the waves of light met each other to become a standing wave that radiated around the nanowire, which was then imaged by firing a stream of electrons. The electrons either sped up or slowed down while interacting with the wave, allowing the wave to be visualized. But the electrons were able to demonstrate the particle aspect as well, since the change in speed was caused by the electrons hitting the photons, or light particles.
Lead researcher Fabrizio Carbone said, "This experiment demonstrates that, for the first time ever, we can film quantum mechanics-and its paradoxical nature-directly."