daoxingyoustudent

First class of school.

As soon as Fang Chen walked into the classroom, the students' eyes shone with excitement and they shouted "Hello, teacher" one after another.

Smiling and nodding to everyone, Fang Chen pressed his hands to ask everyone to calm down.

Some students said aggrievedly: "Teacher, we thought you wouldn't teach us anymore!"

"How could it be? The ancients said - it's not satisfying to acquire talented people and teach them. How could I be willing to leave you?"

Fang Chen was joking, but he was filled with emotion in his heart.

Lowering his head and lowering his eyes, he turned on the equipment on the multimedia podium, hiding all his emotions, and then started class.

In the first class, we can’t just talk about watercolor yet, we have to talk about the basic knowledge of color first.

Fang Chen briefly reviewed and summarized the content of the previous semester, and then said: "So, this semester, we will move from the kingdom of black and white to the world of color.

The world we live in is a colorful world. Dawn, dusk, rain and sunshine, the cycle of the four seasons, the sky and the earth, mountains and rivers, flowers and trees, the colors in the many scenes of nature are like flowing curtains, presenting endless beauty. So, how is color produced? "

The students looked confused and exchanged glances with each other. They had never thought of this.

"Color comes from light. Without light, there would be no sense of color. So, what is light?" Fang Chen asked again.

"Light is actually a kind of electromagnetic wave. The wavelength range of electromagnetic waves is very wide." As he spoke, Fang Chen projected an electromagnetic wave table, which was arranged: cosmic rays, X-rays, ultraviolet rays, visible light, infrared rays, radar waves, radio waves, AC waves, etc.

"In this electromagnetic wave table, only electromagnetic waves with wavelengths between 380 nanometers and 780 nanometers can be seen by the human eye. The electromagnetic waves of this wavelength are called the visible spectrum, or light. The other wavelengths of electromagnetic waves are all visible to the human eye. Invisible light is generally called invisible light. For example: electromagnetic waves longer than 780 nanometers are called infrared rays, and electromagnetic waves shorter than 380 nanometers are called ultraviolet rays." Fang Chen pointed at the wavelength values ​​with the light pen, and Fang Chen kept talking.

The students were a little confused: Why did the teacher teach physics?

Facing the confused looks of the students, Fang Chen paused and then said:

"The British physicist Newton once used a prism to decompose the white light of the sun into seven color bands of red, orange, yellow, green, cyan, indigo, and violet. This process is called dispersion. Rainbows are caused by the numerous small water droplets in the air after the rain. The small water droplets gathered together act like a prism, causing the dispersion of the sun's white light."

Immediately, Fang Chen projected a wavelength table of various colors of the rainbow.

"So: color comes from light." The students were still a little confused. This knowledge was a bit boring! Fang Chen knew very well that if these basic knowledge of color were not explained clearly, in the future the students' watercolor paintings would be very conceptual and general, with single and boring colors, so he continued to explain them firmly.

"White light shines on everything. Because the surfaces of different objects are different, the reflected colored light is also different. In other words, different objects have different reflection rhythms, which are called pigments.

For example, the reflective rhythm of a blue object can reflect blue light, which means that its reflective rhythm can reflect electromagnetic waves of 450-480 nanometers. If blue light shines on it, a synchronous resonance will occur, causing the blue light to be reflected back. So we see to it's blue color. The same goes for other colors.

The students' eyes widened. It turns out that color is really related to physics!

A student in a black windbreaker raised his hand and asked, "Except these seven colors, where did the other colors come from?"

"This is a very good question." Fang Chen looked at the disciple with approval and continued:

"The reflective rhythm of some objects' surfaces is 450-550 nanometers, which means they can reflect both blue light and green light. So what will happen?"

"That's blue-green." The students answered affirmatively.

"Yes! Very good. That's how the colors are produced."

"So what would happen if there were surfaces that could reflect all wavelengths of visible light?"

"Is it white?" A student whispered.

"Yes! That's right." Fang Chen affirmed, and then asked another question: "Where did the black color on the windbreakers worn by our classmates come from?"

The student in black couldn't help but widen his eyes: "Black? It's dyed."

Fang Chen smiled and said, "Based on daily life, your answer is correct. But based on the principle of color, your answer is incomplete. Black, a dye substance, cannot reflect a certain color of light purely, and white When light shines on it, all wavelengths of color light cannot produce synchronized resonance returns, that is to say, they are all absorbed, so it appears black. But the absorbed light will be converted into heat, which is the phenomenon of black light absorption."

"Please think about it further: What color will you get when the seven colors of red, orange, yellow, green, cyan, indigo and purple are fully mixed?"

The students talked a lot and couldn't agree on what to do.

"Then open your colors, mix them up, and try them out."

Soon, the result came out. It was a dark color, and everyone's color was different, but it was not pure black.

"Theoretically, after these seven colors are fully mixed, black should be obtained. However, because the pigment is diluted with water, and the proportions will have some errors, true black cannot be obtained."

"Let's use these three colors, red, yellow, and blue, and mix them to see what colors come out."

"Hey, it's still the same color."

…………

Once the obstacle of "light and color" is removed, the subsequent three primary colors and three secondary colors, complex colors, three elements of color, color warmth and hue, etc., these color knowledge can be easily explained.

The school bell rang.

Fang Chen took a sip of water and just put down the cup.

The class representative came over and asked a little embarrassedly: "Teacher, when will the drawing for the final exam of last semester be distributed?"

Fang Chen hesitated for a moment and asked, "Didn't the examiner give it to you?"

Art is an examination course, and it involves drawing. There is no need to keep papers, so the scores will be returned to the students after the scores are judged.

The class representative shook his head: "I haven't handed it out, and I haven't handed out the two previous assignments either."

Fang Chen was stunned. She was suddenly asked to hand it over to the studio last semester. At that time, there were some student assignments in the studio that had not been handed out. When handing over, Yu Meifang said that the teacher who took over the class would be responsible for handing them out. Thinking of this, I quickly asked: "Who gave you the last class last semester? Who took the exam?"

"Teacher Wan Fangfang, and Teacher Chen Gaofeng." The class representative said, turning his eyes to the student next to him. The student who was listening attentively now nodded in agreement.

Fang Chen’s head is so big!

After class, Fang Chen hurried to the department office to find Yu Meifang.

As soon as she entered the corridor, she heard Yu Meifang's loud and wanton laughter.