Researchers from University of British Columbia (UBC) learn the mechanism of momentum in light
Light has momentum however, the exact nature of interaction of light with matter has not been understood. Now, a research from University of British Columbia Okanagan campus published in Nature Communications on August 21, 2018, reported the mechanism of momentum in light. According to Johannes Kepler, German astronomer and mathematician, in 1619, a comet’s tail always points away from the Sun due to pressure from sunlight. James Clerk Maxwell in 1873 predicted the momentum of the electromagnetic fields of light to be responsible for the radiation pressure.
The current research conducted by engineering professor Kenneth Chau with his international research team from Slovenia and Brazil, constructed a special mirror fitted with acoustic sensors and heat shielding to study the momentum of electromagnetic waves. Extremely weak interactions between light photons were measured by the researchers and the interface and the background noise was maintained to a minimum with the help of heat shielding. The mirror was bombarded with laser pulses and the sound sensors detected the elastic waves when the waves moved across the surface of the mirror.
“We can’t directly measure photon momentum, so our approach was to detect its effect on a mirror by ‘listening’ to the elastic waves that traveled through it,” says Chau. “We were able to trace the features of those waves back to the momentum residing in the light pulse itself, which opens the door to finally defining and modelling how light momentum exists inside materials.”
The findings help in understanding the fundamental nature of light and the mechanism of interaction of flight with light. Moreover, the research can aid in practical applications of radiation pressure. The research was funded by the Natural Sciences and Engineering Research Council of Canada, the Slovenian Research Agency, The Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Brazil, National Council for Scientific and Technological Development, and Fundação Araucária.