Everyone of us have a blind spot which is a small portion within the visual field of every eye where the optic nerve and blood vessels leave the eyeball. Optic nerve is connected to brain ehich carries images of what we see.
The amount of water vapor in the air is called Humidity. The amount of water vapor that air acn hold depends on the temperature of the air. The amount of water vapor in the air as compared with the amount of water that the air could hold is called Relative humidity.