Laser Hazard

As a physics teacher, I clearly understand the potential danger in using laser. The power of ordinary laser pointers is large enough to hurt eyes in a few seconds if direct laser beam is shone on the eyes. The damage is Irreversible! The green laser pointers used in stargazing are much more powerful than that of ordinary laser pointers. Usually the power of a green laser is larger than 10mW. The power of ordinary laser pointer is usually less than 1mW. One can imagine what will happen if green laser beam is directly shone on eyes! Even the scattered light may hurt your eyes. It is a good practice to turn on the green laser at a level higher than the eye level. In addition, I am used to standing behind the one who are using the laser. Last night I encountered a very dangerous situation. As usual I stand behind the one who are using the green laser. He was shining the laser beam to the eyepiece and the laser beam came out from the objective. Ah.. This was a new method to test the direction of the telescope. While I was watching at the back of him, the scatter laser beam shone on my eyes! Gosh! Since the field was very dark. I went to the toilet and see if any problem with my eyes! God bless! Yeah! There was no blind spot visually! I guess most eyepiece cases are black in color. This lowered the intensity of the scattered laser beam. If not, the result would be disastrous! Well! After this bad experience, I have concluded the followings precautions:
1. Make sure no people in the direction of fire.
2. Shorten the fire time when you fire the laser.
3. Don’t wear shiny watches or decorations on your hands when you operate lasers.
4. Don’t look at the area around the laser pointer, even it is not directed at you.
5. Stand sideway to the one who is operating the laser.

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