Brain misunderstanding afterimage
The time resolution of the human brain is 1/50 to 1/100 second. This will not interfere with your daily life. Lights that flash faster than this appear to be on continuously. This is called an afterimage.
Experiment 1: Let's make letters with afterimages.
you need : Fan with LED light (about 3000 yen in Akihabara etc.)
The wings do not rotate very fast, so the letters appear to flash. I bought this fan at a shop called "Akibao" for 2000 yen. You can write various characters and symbols from your PC. The mechanism is that 11 LEDs arranged vertically rotate while blinking repeatedly.
For example, if you want to make a character with 9 LEDs arranged vertically, instruct the LED to light up in the black part of the picture on the left and turn it off with a white frame. You can also change or move the letters. This is a terrifying product because a 2000 yen fan will do this. A long time ago, it was sold as a souvenir as a display to be shaken at Disneyland.
Experiment 2: Let's overlay two pictures with an afterimage
Draw a bird picture and a birdcage on the front and back of the uchiwa. If you rotate it quickly, it looks like a bird is in the birdcage.
This has an afterimage, but the brain has the property of associating with a series of pictures. A flip book is an example. This is called scanning.
Experiment 3: Let's spin Benham's top
It is a top sold by a toy store called Benham in the 19th century. Paint half black and add lines at 45 ° each. You can see various colors when rotating. The principle of color development seems to be due to the blinking of the black and white parts. I don't seem to know the details.
