"Before that, I want to tell you a truth. A convex lens can gather light, while a concave lens can disperse the light." Han Du picked up the bottle and gestured in front of everyone, and said: "When this bottle is empty, It can't gather light because it's not a convex lens yet."
As he spoke, he placed the empty bottle on top of a pile of hay, but no matter how Handu adjusted the distance between the bottle and the hay, no light spot appeared on the hay.
"But as long as you fill it with water, it will become a convex lens, which can concentrate the sunlight." As he said this, Han Du filled the bottle with water, then placed the bottle above the hay again, and slowly adjusted it A short distance away, a bright light spot appeared on the hay.
Han Du kept his distance, and soon the hay began to smoke, and after a while, flames appeared and burned.
"The temperature of the light gathered in this way is very high, enough to ignite easily flammable things such as hay."
Lao Zhu squatted down next to Han Du, reached out to take the bottle, and asked: "So, starting a fire like this actually has nothing to do with water?"
Han Du nodded and said, "Yes, any convex lens can be enlarged to gather sunlight and ignite the flame. Convex lenses made of glass can also be used."
After saying that, Han Du took out another convex lens and handed it to Lao Zhu.
After Lao Zhu took it, he followed Han Du's example and adjusted the distance, and a small light spot suddenly appeared on the ground. Remaining still, a dead leaf that the light spot hit soon started to smoke. It was just because there were too few dead leaves that it didn't burn.
Han Du diligently grabbed a handful of hay from the ground and placed it under the convex lens, and soon flames burst out and burned.
Lao Zhu stood together holding the convex lens and said with a sigh: "The world is full of wonders. Who could have thought that a piece of glass can ignite fire?"
Later, Lao Zhu asked again: "Which branch of knowledge is this in mathematics, physics and chemistry?"
Han Du smiled and said: "Physics is a small branch of optics."
"What about cement?" Lao Zhu asked again.
"Chemistry is a branch of inorganic chemistry." Han Du said truthfully.
Lao Zhu
Nodding, he naturally put the convex lens into his arms, patted Han Du on the shoulder, and praised, "Teach well, and if you need anything, just tell me directly. I only hope that you can do your best to teach them knowledge and train them Become a talented person."
Han Du nodded solemnly, turned his back to the student and bowed secretly to Lao Zhu.
Two days later, the college examination was held as scheduled. On this day, the weather was also beautiful, and the sun was shining brightly from early in the morning. In just three days, more than 800 Gong students signed up to take the academy exam.
Han Du cleared out the square in the back half of the academy, and it suddenly accommodated more than 800 people taking exams at the same time.
There are only two subjects in the examination, arithmetic and classics. Arithmetic is just a topic in various arithmetic scriptures, it has just been changed. If you are involved in arithmetic and can draw inferences from one instance, you will naturally be able to answer it easily.
The title of Jingyi was given by Fang Xiaoru himself, according to his words. Since he wanted him to teach the classics and meanings, he naturally wanted to know the level of each of these Gongsheng's classics and meanings.
The academy examination did not take two days like the Imperial College examination, but ended in one day.
In order to seize the time and not make Gong students wait any longer, the academy organized and started marking the papers that night. Han Jingyun and Mr. Jin, as well as students from the academy, were helping to mark the arithmetic exam papers, so they went very quickly.
On the contrary, the review of the classics and meanings by Han Du and Fang Xiaoru progressed slowly. The main reason is that Fang Xiaoru is relatively slow. He has to carefully consider every exam paper, which naturally wastes a lot of time.
"Old Fang, you can't do this." Han Du sighed helplessly.
Fang Xiaoru raised his eyes and glanced at Han Du, ignored him, and turned his attention to the examination paper in front of him.
Han Du had no choice but to shake his head and persuade: "With your attainments, you can easily tell the quality of the test paper at a glance. Why do you need to read it word by word like this?"
Fang Xiaoru disagreed with Han Du's words and said: "It's not easy for these tribute students to come all the way to the capital, and you only called 300 people into the academy. If I, as a teacher, don't look carefully, wouldn't I betray their trust?"
"But if you review like this, I'm afraid we'll have to wait until tomorrow
Now, do you still want to go to bed? "What Han Du likes most is working hard all day long, and what he hates most is staying up late without rest.
"I'm not going to rest tonight. I'm going to review until dawn."
Han Du was so speechless by Fang Xiaoru that he almost lost his temper and logged off. After he recovered, Han Du stopped nagging Fang Xiaoru, fearing that instead of dying of exhaustion, he would be pissed to death by him.
And since Fang Xiaoru didn't go to rest, Han Du didn't have the shame to leave him here alone and went to sleep by himself. Therefore, even if his eyes turned red, Han Du could only stay with Fang Xiaoru until dawn.
On that day, the merits of more than 800 tribute students were sorted out one by one, and the academy directly announced the recruitment of 300 people.
Han Du didn't even watch the most lively announcement of the results, so he went back to his room in the academy, fell on the bed, covered his head and fell asleep.
Although the academy called for 300 people, due to various reasons, only 216 people finally entered the academy to study. Others gave up this opportunity for various reasons.
After Han Du learned about it, he didn't care. If you don't want to come, don't come. Now the academy has no real achievements, so some people don't trust it very much. This is normal. When the academy's record comes out in the future, these people will regret it.
Not only Han Du, but also Mr. Jin and Fang Xiaoru did not express anything about this.
However, Han Jingyun felt very unhappy about this. She felt that her mathematical attainments were enough to be the ancestor of these people. Now that she is lowering her stature to teach in person, there are still people who are not willing?
"These blind things really piss me off." Han Jingyun's pretty face was cold, and she slapped her angry little hand on the table, which was so painful that she almost shed tears.
Seeing this, Han Du could only comfort him: "Forget it, don't get angry with these people, it's not worth it. There are always too few smart people in this world, and there are too many fools who follow the wind. Don't you think you will do it when you meet a fool? Want to argue with him?"
Han Jingyun felt hurt and angry, so he simply stamped his feet and turned around and left.
The academy originally recruited 300 people, but only about 200 were recruited. Naturally, the academy was not very satisfied.
But even so, there are still people who are full of prejudice and even resentment towards the academy's practices.
