Helicopter rotors spin at around 300RPM. Now for the naked eye they look like transparent, like if the rotors were not even there.
This is said to be because the rotor spins so fast, that our eyes cant catch up to the angular velocity of the rotor.
So this way the rotor becomes invisible for our eyes, and the whole area where the rotors spin becomes transparent.
But light is much faster then the rotors, so basically for light, the rotors are relatively slow, like 0.00001c, and therefore if we use a camera that can catch up to 300RPM speeds, the video we would record would show the rotors simply spinning fast, and the same way if our eyes could catch up to 300RPM speeds, we could simply see the rotor spin fast.
But if the rotor spins so fast, and our eyes can't catch up to that speed, then shouldn't the rotor area be opaque, a full opaque circle, like if there was rotors all around?
Our eyes should see photons coming from the rotor at all angles, and since our eyes are so slow, they should catch all frames of the rotor being at all angles at the same time. This way the rotor would seem to be a full circle opaque.
Why do we see helicopter rotors to be transparent?
Why do we not see a full circle (since it spins so fast compared to our eyes capabilities) of the rotor being opaque?