• Einstein’s Extraordinary Year
    Awake!—2005 | September 8

    • Unlocking the Secrets of Light

      Einstein’s paper published in March 1905 uncovered some secrets about the nature of light. Scientists had already discovered that as light travels through space, it seems to behave much like waves of water rippling across a pond. However, the wave theory could not explain why dim blue light generates an electric current when it strikes certain metals, whereas bright red light fails to do so. Einstein’s paper helped to explain this so-called photoelectric effect.

      Einstein argued that light can at times be considered to consist of small packets of energy, later called photons. When these photons are of the right energy level, or color, they can dislodge electrons from the atoms of some metals. (Photons of red light are too weak to do the job.) This interaction causes an electric current to flow in the material. Modern inventions such as television camera tubes, solar power cells, and photographic light meters all relate to Einstein’s description of the photoelectric effect.

      Einstein won the 1921 Nobel Prize for Physics for his way of explaining light. His paper helped lead the way to a new field of science called quantum theory. In turn, quantum theory laid the foundation for a host of applications including nuclear science, electronics, and nanotechnology.