Chapter 764: holiday!

"Shanchang, in that case, I can say that I have succeeded~? Then what you promised me at the beginning is counted!"
Hearing Li Zexuan's affirmation, Mo Lingwei became excited and said quickly.
Li Zexuan chuckles and said, "Hehe, this is far from success! What I said at the beginning was that I asked you to build an astronomical telescope. Do you think Miss Mo can see the moon in the sky with this little thing~?"
Mo Lingwei blinked curiously and said: "Why can't it work? I can see far away with my clairvoyance, can't I take it to see the moon~?"
"Of course not!"
Seeing Yan Shaoning next to him was also confused. Li Zexuan had to patiently explain to him: "I told you before that the magnification of this clairvoyance is related to the focal length of the objective lens and eyepiece. The clairvoyance you are doing now has the highest magnification. It’s about seven to eight times as much, that is to say, if you look at one hundred feet away with this one, you will be looking at a distance similar to about ten to twelve feet, and the moon is about 880,000 away from us. Here, you said that with this thing, we can see what the moon looks like?"
(The moon is usually more than 400,000 kilometers away from the earth. In the Tang Dynasty, Li Shimin's double steps (one step on each of the left and right feet) were used as the size standard, called "step", and three hundred steps were defined as one mile, one " One-fifth of the "step" is one chi. In the Tang Dynasty, the Chihe is now 0303 meters, and one li is 454 meters. The distance between the earth and the moon is almost equivalent to 880,000 li in the Tang Dynasty)
"Eight eighty thousand miles? How far is that~?"
After the two listened, they were speechless. Yan Shaoning thought for a while and asked: "Xiao Xuan, according to your opinion, do we only need to increase the magnification of the clairvoyance~?"
Li Zexuan pondered his chin and replied, "Well, but it's not just a matter of increasing the magnification. When the magnification is too high, the final image formed by the clairvoyance will be distorted. You must find a way to reduce the problem of imaging distortion, or zoom in. No matter how high the multiple is, it’s no use~!"
Mo Lingwei frowned, wondering: "Shan Chang, what is imaging distortion?"
It's no wonder that she is ignorant, mainly because this knowledge has not been mentioned in the first volume of physics textbook.
Li Zexuan organized some language and explained: "I have told you about the imaging principle of convex lenses. In fact, those are the cases where the light is close to the central optical axis, but in fact there is always a part of the light that is not close to the central optical axis. They are on the edge of the lens. Compared with the actual object, the final image formed by this part of the light is deformed to a certain extent. I call this distortion!
For clairvoyance, if you want to obtain a higher magnification, the length of its overall optical path will become longer. At this time, after a small distortion passes through such a long optical system, the distortion will be even greater! So when you increase the magnification of clairvoyance in the future, don't neglect the image quality! According to my experience, as long as you can guarantee a magnification of more than 30 times, you can basically meet the requirements of astronomical observation! "
Li Zexuan is very familiar with telescopes. When he was in high school, a buddy in his dormitory brought a telescope. He called it to look at the scenery opposite the dormitory, but the opposite was the female dormitory. In the end, Skynet was restored, and it was not leaking. The boy's telescope was confiscated by the head teacher who suddenly checked the bed.
When he was in college, he benefited from the school’s geographical location. On an open day of a planetarium in the capital, he spent thirty-five yuan to go in for a walk. It can be considered that he has personally used astronomical telescopes, and his undergraduate and graduate students The major he learned during the period involved a considerable part of optical knowledge, and even personally polished the lens during the internship. In the era of the Tang Dynasty, he can be called an expert in optics! This is also why he can explain to Mo Lingwei and Yan Shaoning so well.
"Then Xiaoxuan, how do we solve the imaging distortion~?"
To be honest, Yan Shaoning is not shocked at all about the endless source of novel knowledge that always pops out of Li Zexuan's brain, because he has long been numbed by shock. The more important thing than shock is that he needs to try his best to absorb Li Zexuan. New knowledge revealed.
"This is difficult!"
Li Zexuan shook his head complicatedly. For the imaging distortion and chromatic aberration of the lens, the method of cemented lens is often used in modern times. By fixing two or more lenses with photosensitive glue, then baking with ultraviolet light, after two After the curing process, a set of cemented lenses can be obtained.
In some modern precision optical components, such as microscope objectives, telescope eyepieces, etc., all of which are used are lens groups cemented by photosensitive glue. If only a simple convex lens or concave lens is used, it is difficult to obtain better imaging results.
However, in this era of extremely backward basic science, it is no different from a dream to control imaging distortion like modern optical lens companies. Not to mention that there is no photosensitive glue, and there is no way to get pure ultraviolet light alone~www.mtlnovel .com~ In this case, how can a cemented lens group be made!
"Although it is difficult, you can think of a way to replace a simple single lens with a lens group composed of many small lenses that are closely spaced, and keep the overall imaging optical path unchanged! This may result in some The difference~!"
After thinking for a long time, Li Zexuan could only use a dead horse as a living horse doctor and said.
Both Yan Shaoning and Mo Lingwei were lost in thought.
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"Clang, clang~!"
With a burst of "clear" gongs and drums, Yanhuang Academy's training today finally ended. Qin Qiong (who was late in the morning because of the heavy rain), as the Academy's military training chief instructor, decisively blew the horn of orders.
"After school~!"
The enthusiasm of the students for training today is very high, there is no need to deliberately embarrass people on this, so Qin Qiong's impression of the instructors is quite good. As soon as school is over, let the students go to school decisively, without any delay!
"Oh~! It's a holiday~!"
"Finally I can go home to sleep in~!"
"Haha~! I will definitely not come out in these two days! It is really not easy to put a day or two in the academy~!"
The students burst into cheers, and then Yanhuang Academy became a sea of ​​joy, and cheers could be heard everywhere. The students ran back to the dormitory like a gust of wind, then rushed out of the dormitory, out of the gate of the academy, and headed directly to Chang'an City below the mountain.
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