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Question
I was once pointed in the eye with a laser pointer and it blurred my vision for minutes and I had these residual figures still in my field of vision during those minutes. So how can a light emitter have this powerful effect on the eye when other kind of light emitters like lamps do nothing like that to an eye?

Answer
Hello Mika,

It is a matter of the intensity that entered your eyeball. The sun is very intense and looking at the sun, even at a solar eclipse when most of the sun is covered by the moon, can cause permanent eye damage. Open this website:
http://en.wikipedia.org/wiki/Intensity_(physics)
This is a quote from that website. "In physics, intensity is the power transferred per unit area. In the SI system, it has units watts per metre squared (W/m^2)."

The power from a laser is concentrated in a small area. So a measurement of the watts/metre^2 would be a large number. The light bulb in a lamp might put out more total watts than the laser did, but the lasers watts all went in the same direction while the light from a lamp hits all the m^2 in the room.

I hope this helps,
Steve

Physics

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Steve Johnson

Expertise

I would be delighted to help with questions up through the first year of college Physics. Particularly Electricity, Electronics and Newtonian Mechanics (motion, acceleration etc.). I decline questions on relativity and Atomic Physics. I also could discuss the Space Shuttle and space flight in general.

Experience

I have a BS in Physics and an MS in Electrical Engineering. I am retired now. My professional career was in Electrical Engineering with considerable time spent working with accelerometers, gyroscopes and flight dynamics (Physics related topics) while working on the Space Shuttle. I gave formal classroom lessons to technical co-workers periodically over a several year period.

Education/Credentials
BS Physics, North Dakota State University
MS Electrical Engineering, North Dakota State University

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