70: Learn to make a telescope 3

The one Fang Mu thought of was precisely the Galilean Telescope, which is composed of one convex lens and one concave lens.

"Fang Mu, that's a good question. I also made a Telescope combining a convex lens and a concave lens, with the convex lens as the objective and the concave lens as the eyepiece.

Light rays from distant objects, after passing through the objective, converge very close to its rear focal point, outside of it, forming an inverted, diminished real image. This real image then acts as the object for the eyepiece, which forms an upright, magnified virtual image.

You can directly see an upright image. Although this Telescope can produce an upright image directly, its field of view will be relatively small."

After speaking, Xu Bai drew another light path diagram.

"Do you have any other questions?"

The three exchanged glances, neither nodding nor shaking their heads, feeling like they half-understood.

If they said they understood, they didn't feel like they fully grasped it. If they said they didn't understand, the light path diagram was very clear and made sense.

Xu Bai noticed their hesitation and didn't force them to think of questions. He encouraged them, saying, "You can try to make one, and then adjust it if it's wrong. You can also ask me if you have any questions while making it. Because no matter how much you listen, if you don't do it yourself, you won't know what you don't understand."

The three sighed in relief. They couldn't help it; even though they were good students, they still got a little nervous when a teacher asked questions.

Xu Bai put down the chalk in his hand, picked up the newspaper again to read it, and let them practice making while looking at the light path diagram.

He didn't know when the person who invited him to join the Card Maker Guild would arrive. Sigh, Xu Bai had already flipped through the recent newspapers and was eager to know what content the Card Maker Guild's newspaper would have...

"Hello, are you Brother Xu Bai?"

Just as Xu Bai was dozing off, a question came to his ears.

Xu Bai opened his eyes and looked over. Before him was a tall man in a college uniform, with slightly dark skin, eyes somewhat like rye bread, and very white teeth, so much so that he could endorse toothpaste when he smiled.

Before Xu Bai could answer, Zhao Zixuan saw his deskmate and quickly stood up to introduce him.

"Brother Xu, this is Li Lan, my deskmate whom I told you about, who wants to learn how to make a Magnifying Glass. Li Lan, this is Brother Xu."

"Hello, please come in directly, no need to be polite. You can sit here, and I'll explain the principle of the Magnifying Glass to you."

Xu Bai gave Li Lan a friendly smile and pulled out a stool, placing it in the spot closer to him.

The seating arrangement was such that Zhao Zixuan and the other two sat furthest inside, then there was Xu Le's play area in the middle, and after that were Li Lan and Xu Bai.

This was to prevent Li Lan from knowing other things, as they weren't very familiar yet and needed some time to get to know each other.

"Okay, Brother Xu, these are some fruits I brought for you. I'll put them here."

Children from poor families learn to be self-reliant early. They always want to show their appreciation for others' kindness.

"Okay, Zi Xuan, wash these and also give some to Fang Mu and the other two. Let's all eat and relax."

Xu Bai didn't refuse Li Lan's kind offer. After instructing Zhao Zixuan, he continued.

"Li Lan, don't be so polite later either. I'll be relying on you to look after this shop on Saturdays and Sundays."

"Okay, Brother Xu, I will help you look after the shop well."

...The two exchanged a few pleasantries and then got straight to the point. Xu Bai began teaching Li Lan some knowledge about the Magnifying Glass.