Scientists Finally Understand How Grapes Produce Plasma In A Microwave


A Trent University physicist demystifies the science behind a party trick of exploding grapes in a microwave and explains how it can pave way for nanophotonics.

Aaron D. Slepkov, the study lead author, explains that halved grapes that are still connected by their skin ignite when exposed to microwave radiation due to hotspots of electromagnetism. The study findings published in the journal Proceedings of the National Academy of Sciences not only solve this mystery but also reveals that any water-based spheres the size of a grape can replicate the effects.

Size Matters

Pablo Bianucci, study co-author from Concordia University Montreal, tells Popular Mechanics that contrary to popular belief, neither halved grapes nor the skin-bridge is required for it to burst into plasma.

Instead, Bianucci, Slepkov, and Hamza Khattak, an undergraduate student from Trent University, discovered that the effect can be replicated with any water-based and grape-sized sphere including quail eggs, blackberries, olives, and even hydrogel beads.

Bianucci further explained that the size and composition of grapes in terms of water content determines how they interact with microwave radiation.

"There is a lucky coincidence in the fact that the grapes have both the right composition (mostly water) and size," he said, adding that a single wavelength of microwave radiation fits almost entirely into the grape, meaning the grape can "trap" microwaves.

The hotspots created as a result have an amplified electromagnetic field in between the grapes, which leads to the generation of plasma, Bianucci revealed.

Exciting Findings And Its Significance

The study findings also discovered that irradiated whole grapes are capable of producing plasma, as long as they are touching each other. The hotspots, in this case, appear where they meet, producing an electromagnetic field that is capable of ripping the grape's surface.

The spark that releases the molecule in the air absorbs microwave energy as they lose electrons, resulting in a flash of light, known as plasma, that may be seen rising up from the grape.

Slepkov explained that the discovery is exciting because the water has an unexpected quality that allows it to draw in the microwave radiation and compress it.

The scientists believe that if they are able to find a similar material that works for light the same way it works for water, then it is possible to focus light in very tight spaces. The study of light on a tiny scale is known as nanophotonics that can have ground-breaking implications in the field of national security, space travel, and surgery.

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