Many diseases, including COVID-19, spread because the virus

Last updated: 7/28/2022

Many diseases, including COVID-19, spread because the virus is carried by tiny particles (diameter 10 µm) suspended in air, emitted when people sneeze, cough, exhale, and talk. A recent study found that these suspended particles have an effective diffusion coefficient of 1.6 x 10-³ m²/s. We have often been advised to stay 6 feet (1.83 m) away from other people in order to reduce the likelihood of contracting COVID-19. For the given diffusion coefficient, how much time would it take for these particles to diffuse this distance? Assume 3D diffusion.