When a sparkler is twirled rapidly, people perceive a circle of light. This occurs because:. a. the trail you see is caused by sparks left behind from the sparkler. b. due to its differing wavelengths, the light from the sparkler continues to radiate for about a second after it goes out. c. the length of iconic memory (the persistence of vision) is about a fraction of a second. d. Gestalt principles work to complete the circle in our minds.

the length of iconic memory (the persistence of vision) is about one-third of a second

Explanation:

The light perceived after a twirl is cause by the lack of reaction of the eye to quickly react when our view has changed. This then cause the former view to linger for a fraction of a second. This is called persistence of vision. Which is the visual perception of an object does not stops for some time even if the ray of light before it has stopped from entering the eye.

As we all know, fireworks is a combustion reaction with light and heat. The various stars also in the fireworks are a results of the combustion of the chemicals (such as copper, barium) which produces different colors. Therefore, it is when these chemicals are heated, that they change from solid to gas thereby causing the explosions that result into stars.