Forces from photons: Moving matter with light(光子的力学效应)
实验单元主要内容概述:
Despite what you might think from experience in everyday life, light actually exerts measurable forces on objects - it can push, pull, turn, and trap. Science fiction movies show it all the time, but we will show how can it work in real life. In fact, this force-generating ability forms the basis of a crucial technique for biophysical research called optical tweezers (or traps) that has made fundamental discoveries in many microscopic and even atomic systems. Professor Arthur Ashkin was awarded the Nobel prize in Physics in 2018 for the first demonstration of the extraordinary ability of light. We will follow Professor Ashkin’s footsteps with hands-on experiences to appreciate the simplicity, beauty, and ultimately, the incredible power of being able to control material with light. There will be three experiments in this module. The first experiment will be to show that a beam of laser light can push water droplets in air, as first described by Ashkin. We will assemble the simple device, and then measure the velocity of the droplets at different laser powers to compare with expected values. The second experiment will be to assemble an optical tweezers and then use the device to manipulate microscopic beads in solution. We will also measure the strength of the tweezers, which is necessary to know for force measurements. Finally, the third experiment will be to capture free swimming bacteria using the optical tweezers and measure the force that the bacteria actually generate with their remarkable nanometer-sized motor.