Surely it happened to everyone that you were looking at a car that was driving forward, and you got the feeling that the wheels were moving in the opposite direction or not moving at all. Or, for example, in some movie a helicopter flies, and it seems that the blades do not rotate. This is the stroboscopic effect, which is a rather difficult concept in the field of physics. If you delve into the definition, then from the Greek language this phrase will mean the next set of concepts “circling” and “watching” (also can be translated as “whirlwind” and “consider”). And this is a classic optical illusion, which is due to a number of factors.
What is this effect?
The stroboscopic effect is nothing more than an optical illusion that occurs when the distorted perception of moving parts. And one cannot fail to say that in physics there are two main types of this effect:
1. The first type is characterized by the fact that when observing the rapidly changing individual phases of motion, the illusion of continuous motion arises. This is associated with the characteristics of visual perception. So, for example, if the time between appearances of some individual images is much less than the gap, then the images merge, and the movement is perceived as continuous. It is on this effect that motion in cinema is built, provided that the frequency of filming and projection is approximately equal to the frequency of the ongoing process.
2. This effect of the second type implies that under certain specific conditions there will be an illusion of peace of the object, which is actually moving, and the example with a helicopter determines exactly this type of strobe effect. But here a special role is played by lighting.
Everyone actually observed such optical illusions, just someone does not pay attention to it, and someone simply does not explain the physical basis for the occurrence of this effect. Nevertheless, difficulties in the perception of such actions are also caused by a number of biological factors, in particular, we are talking about the features of building the visual organ and its perception of the surrounding reality - this is called inertia of vision.
Vivid examples of this effect in real life
In fact, if we talk about the stroboscopic effect and where it can be observed in real life, it’s rather difficult to give examples. And the most obvious example that can be seen by everyone is a disco. How does this effect appear on the dance floor? Naturally, the clubs have special lighting and lots of mirrors. All this contributes to the fact that when people dance, there is a feeling that they are moving like robots. Naturally, this is due precisely to the flickering of light and to the peculiarities of its perception by the human organ of vision.
Also, if you have a slow-motion camera, you can observe the stroboscopic effect if you remove the dripping water from the tap. As a result, you will see that one drop happened with certain passages at all intervals, and fell, as it seems to us, smoothly.
Quite a few examples of this effect are reproduced by physicists in the laboratory. To do this, they reproduce a certain light with pulsed sources, with the ability to adjust the frequency - these are strobe lights. So, in these studies, you can observe, for example, the features of the movement of the fan blades. Under specific lighting conditions, there may be a feeling that the blades move in different directions with a certain frequency or even become motionless. Also, with the help of a stroboscope, you can observe the movement of the ball and the features of its trajectory. Such an effect and a strobe, in particular, is used not only to determine some theoretical points, but is also useful for the production of certain machine parts.