why cant we see the blades of fan when fan is moving with high speed?

Answer 1

We do see it, but the background image has predominance, so we kind of miss it.

In a three bladed fan, the blades occupy say 10 or 15 percentage of the total blade disc area. At high speeds, persistence of vision for the background dominates as the blades progressively hide only small sections of the disk.

If you use a strobe light of suitable frequency, the blades can be seen quite distinctively.

Answer 2

In Psychology, this is called Perception of Real movement.

The stimulus for observing a motion is an excitation moving across the retina of our eye.

Hence movement can be perceived only by the cooperation of receptor cells that are stimulated in succession.

There are limits to perceived speed.

The second hand of a watch can be seen in motion but the minute hand cannot.

At 2 meters from the eyes the slowest perceptible movement is about 2mm per second.

We can perceive that the blades of fan are moving but the perception is different when it is at rest.

There is a difference in the perception of the blades of a fan and the inability to see flying bullets and the like.

‘The persistence of human vision’ is different and is not connected with the perception of speed.

While seeing motion pictures, the pictures are shown in succession such that we perceive it as if there is no interval of time between successive pictures.

But perception of speed is different. It is about the speed with which object moves, it may be even the speed of a bird or bullet shown in the motion picture.

The persistence of human vision belongs to the time for which the image rests on a particular receptor cell; where as the perception of speed belongs to how sensitive different receptors cells are are active in perceiving the motion.

Answer 3

Our eye cannot detect change in the vision faster than 16 - 20 times a second and this phenomenon is called the persistence of vision. So, only when starting up and slowing down, the fan blades are visible. When it is rotating at a higher speed, the blades cannot be seen individually.

Answer 4

Due to a phenomenon called persistence of vision, when an object flashes before our eyes at a speed faster than one twentieth of a second, we cannot distinguish between the different components(like blades of the fan) and the eyes tend to follow a trail (like the circular trail of the fan).
It's because of the same reason that we see a continuous picture on TV instead of the different images flashed.

Answer 5

Its all about " how do u see ?? "

When u look at anything, a light ray reflect from that thing to the lens of ur eye, then according to the angel of incidence, it reflect on the retina of the eye, after that the retina sends it to the brain, so u can see & know what u r seeing
All that takes time

at high speeds, the speed of receiving the light ray on eye lens then retina then sending to brain doesn't fit with the speed of fan " for example ", so thats the reason u can't see the blades

i hope u got my point

Answer 6

The retina of the eye cannot react fast enough to see the moving blades after they reach a certain speed.

Answer 7

Our eyes are far from perfect. Like many optical illusions, this is just another way our eyes ease us into making things seem less threatening. If you look back and forth at a fan really fast, you can see its blades, but in general our eyes just observe the whole thing at once instead.

Answer 8

Try laying on your back and squinting, now concentrate, also rotate your vision in the opposite direction as the blades.

Answer 9

because its moving at high speed genius!

Answer 10

i hope you heard of the old saying, the hand is faster than the eye. well, so is the fan.