Light, the role of photon
In the last 6th newsletter (16th/May/2019), as I introduced photon and electron, I have mentioned that when the photon which makes up the light hits an object, the electron escapes from the object. For example, if we shoot single photon on a metal plate as shown in the picture, electron is emitted from the collision and we can hear the gunshot like ‘Tang-Tang’ by using speaker if this is repeated. To sum up, I have explained that all things including human beings are made up of atoms and electrons, and light emits the electrons of our bodies.
Arthur Holly Compton(1892-1962) conducted an experiment in which he irradiated X-ray into graphite to observe the changes before and after the experiment in 1923. From this experiment, particle theory was firmly established as it was known that light and particle can be explained by the same concept (light=particle). When X-ray of a constant wavelength is reflected on a material, some are transmitted, some are absorbed, and some are scattered, which is a literally a phenomenon of scattering in several directions.
When the photon collides with a fixed electron, the electron bounces in the upward direction due to this collision, and the photon bounces in the downward direction. The notion that light is wavelength cannot explain this result. If we hit another ball by a billiard ball, it is possible to bend the stopped ball and the moving ball at a certain angle from the straight direction because it is a particle.
In the following newsletter I will explain that light has not only the particles duality but also wave duality.

Sooyoung Moon, Ph D.
Our Healthcare Committee 

Next week's topic : The effects of light on retinal cells

You can find "Interesting Story about Light Science” series on the link below. 
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