3 ms·
the fluid in the human eye is opaque to 1550nm light, so the light can't reach the retina at the back of the eye. So...it'll just fry the front of the eye?
by rhizome 8y ago
the fluid in the human eye is opaque to 1550nm light, so the light can't reach the retina at the back of the eye.
So...it'll just fry the front of the eye?
- ddebernardy 8y agoWater absorbs that wavelength if memory serves me well, so it's more like boil than fry -- kind of like what happens in a microwave oven. But the energy levels involved are so small it shouldn't be a concern.
- saulrh 8y agoThe eye focuses light. Formally, this transforms incoming photons so that their position on the retina is a smooth function of their direction. Diffraction and atmosphere mean a laser will be distributed somewhat in position, so the incoming photons may be spread over a 2mm spot on the front of the eye. However, all of those photons have almost identical direction and end up being concentrated in a single spot on the retina, up to the limits of the eye's optics. 20/20 human vision can resolve down to about .02 of a degree so a point source should be very similar to a .02 degree circle, the visual nerve blind spot is 7.5 degrees wide and is caused by a 1.5mm obstruction on the retina, so a point source like a laser should land in a spot on the retina about .005mm across. 2mm diameter / .005mm diameter is 400 and area is proportional to the square, so this would be something like 160,000x decrease in area with equivalent increase in intensity. Result: Not even enough to warm your skin up but instantly boils a bit of your retina. (I'm rather happy with how well my estimate corresponds to the figure from Wikipedia: "The eye focuses visible and near-infrared light onto the retina. A laser beam can be focused to an intensity on the retina which may be up to 200,000 times higher than at the point where the laser beam enters the eye.")