# Magic of light

On the grand stage, the host is passionate about introducing a magic performer: “It has no flexible hands, but creates brilliant rainbows; it brings us light and creates illusions. It is light!”

With warm applause, the light boarded the stage and began to introduce myself: “I am the fastest thing in the world. The speed in vacuum can approach 300,000 kilometers per second. Although I am spreading in a straight line, when I am When I turned, I became a magician and brought incredible magic performances to the world!”

Uncapable fish
In the cold river, a child is trying to stab the fish in the river with a wooden fork. He aimed at one of the fish and then stabbed it with force, only to find that it could not be penetrated.

It turned out that when the sunlight hitting the fish reflected into the eye, the light had already refracted in the process of leaving the river and entering the air, but the brain believed that the light was traveling in a straight line, so the fish’s real position was in error, and the fish was seen. It will be a little higher than the real fish. If you have been slashing at the “fish”, you can’t stab it.

Refraction of light
Light travels differently in different media. When it is obliquely incident into other transparent media, such as water, it will refract, that is, the direction of light changes. Just as a queue is moving, if the inside player suddenly slows down, the entire team will bend in order to maintain the formation.

Beautiful rainbow
On the stage, the rain sparsely pulled down underground for a while and then stopped. At this point, the light slammed into the place where it had just rained, and there was a rainbow there! The audience was amazed and questioned: “Why is this?”

The light explained to the audience: “After the rain stops, there are many small water droplets in the air. When the light enters these small water droplets, it refracts and then reflects back from the inside of the raindrops. The reflected light is again refracted due to multiple refractions. , so that the various monochromatic lights are clearly separated. The separated monochromatic light enters the human eye and forms a rainbow.”

Spectroscopic phenomenon
White light is composed of seven kinds of monochromatic lights of red, orange, yellow, green, blue, enamel and purple. Since the speed of propagation of each monochromatic light is different, their refractive angles are also different, resulting in entering a medium such as water. The light of each color will be slightly separated.

Mirage illusion
“Look, there is a building in the sky!” A spectator pointed at the sky above the stage and shouted, and other people looked forward.

This illusion is called a mirage, occasionally appearing in calm seas, lakes or deserts, and it is also caused by the refraction of light. When the density of the air changes due to changes in temperature, humidity, etc., the refractive index also changes. In the case of a gradual change in refractive index, light will propagate in a similar curve. Light enters the human eye in a curved way, causing humans to see objects that are otherwise invisible, but the brain thinks that light travels in a straight line, so that the object appears to be in a place where it does not exist.