Photon and Electron
Photon and Electron
Light is the flow of photons, and the elementary particles of light are photons. The photon has no mass and always moves at the speed of the light in a vacuum. As we mentioned in the “Interesting story about Light Science” Vol. 1, Atoms are not only fundamental elements in our world but also in human body. When a photon of light hits an atom then electron is emitted. This phenomenon can be detected by a photomultiplier tube (PMT). 
As shown in the figure, when a photon hits surface of the A plate, such as a gunshot, an electrons will be emitted by collision. Then the emitted electrons will hit the B plate. Therefore, more electrons are emitted by the collision. When, this action is being repeated for 10 times, we can able to hear the sound like “TANG”, “TANG”, through the speaker connected the L plate. This principle not only affects animals and plants, but also human body, especially in eyes. It has diverse effects on child’s myopia to circadian rhythm. 
Furthermore, the effect will be different for each wavelength of lights. Blue light tend to have shorter wavelength than red light so it’s harmful to human-body due to its high energy In particular, excessive blue light induces various side effects such as retinal cell death and biorhythm disturbance rather than complimentary effect. 
How many photons per second will it occur in our home and office lighting? We need a human-friendly light source, light for our health.

Chung H. Lee 
Our Healthcare Committee 
Next week’s topic: Street Light & Breast cancer/Prostate cancer 

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