Friends who have studied physics should all know.

The refractive index of visible light varies in different environments, such as glass, air, water, and so on.

These things have a unified term in concept, which is called a medium.

Nowadays, with the gradual standardization of optical theory research, many junior high school students also understand a truth:

Light can propagate in a medium, and the propagation of light itself does not require a medium.

But don't forget, little Newton is in the year 1665, a period when optical research is still in its early stages.

Therefore, it is completely beyond the scope for little Newton to think of the possibility that the seven colors of light may have different effects in different media with just a few words from Xu Yun in less than half a minute. (Note 1)

Indeed.

At present, little Newton does not know that light itself is a boson and does not need any fermions to propagate. In this era, the top theory of optics for refraction is a mathematical equivalent form derived by Snell, and no one knew it before he died.

It was not until 1678, when Huygens and others reviewed his manuscript, that it was publicly known as the famous Snell's Law.

Before that, it was only derived by Descartes in "Dioptrics".

And there is also a confusing account that no one can explain the truth, which still leads to them sharing the honor of discovering the law of light refraction.

Therefore, although little Newton's expression subconsciously covers the speculation that visible light cannot propagate through a certain "environment", this is a completely understandable situation. To be honest, being able to think of the previous layer is already amazing, okay?

Then looking at the small cluster of colorful light on the ground, little Newton suddenly thought of something else.

He pondered for a few seconds and asked Xu Yun:

"Fat Fish, since sunlight can be dispersed into seven colored lights, are these seven colored lights different?

Also, theoretically, these seven beams of light should be able to be recombined into white light, right?"

Xu Yun twitched his mouth, damn it, he opened his mouth and hit two fatal points again.

But at this time, he had gradually adapted to the abnormal thinking ability of this ancestor, so he quickly adjusted his mentality and said:

"Sorry, Mr. Isaac, I only know the answer to the second question- as long as the conditions are right, the seven-colored light can be recombined into white light."

Little Newton was already interested at this time, his eyes turned around:

"Fat Fish, you said earlier that a prism can also verify the phenomenon of dispersion?"

"That's right, and the effect of a prism is much better than that of a lens."

"Then let's do it again with a prism!"

Little Newton quickly looked around and made a decision:

"I'll go inside to find a prism. I brought back a lot of these things from London a while ago.

You just need to move the table- the tea table in the house will do, put it here."

Xu Yun nodded:

"Understood."

More than ten minutes later.

A table with a diameter of about one meter, several prisms, and a black wooden board were successively placed by the water tank.

A quick look at "pawread.com" will leave you more fulfilled.

Then Xu Yun stood up a prism, skillfully adjusted the angle, and made an OK gesture to little Newton.

After a while.

A cluster of long spectra appeared on the cardboard behind the prism, and it was much clearer than the previous one.

Seeing this, Xu Yun stepped aside, deliberately not making any expressions, wanting to see how far this young version of the ancestor could go without any prompts.

Little Newton walked to the table, leaned over and carefully examined the spectrum.

Then he hesitated for a few seconds and picked up a black cardboard.

He cut out a circle on it and placed it on the outside of the prism, where the light source was coming from.

A large amount of sunlight was blocked by the cardboard, and only a beam of circular light passed through the small hole, and then...

It still formed a long spectrum.

Seeing this situation, little Newton couldn't help but say, "Huh."

For some reason, he suddenly looked at Xu Yun again as if he wanted to talk to someone:

"Fat Fish, have you heard of Mr. Descartes' theory?"

Xu Yun nodded and said:

"Of course I have heard of it. I visited the University of Poitiers once before.

Mr. Descartes believed that the color of light comes from the medium between the light source and the human eye, and has nothing to do with the light source.

The color of light is not an inherent characteristic of light, and he also proposed the theory of light trace transformation."

"You're right, but look here."

Little Newton held a cardboard in one hand and pointed to the projected long spectrum with the other hand:

"According to Mr. Snell's equivalent formula and Mr. Descartes' theory, the circular light beam should form a circular or elliptical spot after passing through the prism.

But after dispersion occurs, the seven-colored light forms a long spectrum...

Could it be that...

Mr. Descartes' theory is flawed?"

After saying this, little Newton thought for a moment, and before Xu Yun could respond, he picked up the cardboard and scissors again and made a smaller hole.

He placed this cardboard behind the first prism, so that he could capture any beam of light in the colored light band using this circular hole. (Little Newton hand-drawn this device before, (DOI) 10.1098/rsta.2014.0213, personally drawn by little Newton. If you are interested, you can take a look. He is really a talented artist.)

Then little Newton waved to Xu Yun, motioning him to come forward:

"Fat Fish, I will report the data, and you will record it."

Xu Yun's pupils slightly contracted, knowing that little Newton was gradually moving towards his ultimate "trap" step by step, but his expression remained unchanged:

"Okay, Mr. Isaac."Subsequently, the two of them each took a pen and paper, and one of them began to calculate the angles.

"Red light, incidence angle i60°, refraction angle β32.2°, reflection angle....."

"Urban management, incidence angle i60°, refraction angle β37.4°....."

"Incidence angle i60°, refraction angle β38.7°....."

Twenty minutes later, four sets of data, 28 times, were recorded.

Different types of light have different refractive indices in optical glass. The deeper reasons involve the relative magnetic permeability μr and the relative permittivity εr. These two constants need to be calculated by Maxwell's equations in the medium, then establish an intuitive model of the interaction between matter and light, deduce the motion equation through linear dissipation force, and then solve his steady state with complex numbers, etc...

However, considering that it's not yet on the shelf and it's inconvenient for PUA readers... cough cough, due to the complexity of the content, everyone only needs to understand the relevant conclusions from a macro perspective.

After all, there were no Maxwell's equations in Little Newton's era, right?

"Purple light 1.532.... Blue 1.528.... Green 1.519..... Yellow 1.517..... Orange 1.514.... Red 1.513..."

Looking at the fixed sets of data in front of him, Little Newton couldn't help but take a deep breath.

It was clear.

The refractive indices of different colored lights are different and remain constant, and the properties of these seven colors of light are different.

From this, we can draw a conclusion:

White light is indeed not a pure light, it is composed of different lights.

And this means...

He is perhaps one step closer to the truth of the world.

At the same time.

Little Newton looked at this light that was divided into seven and yet combined into one, and suddenly thought of something in his mind.

He saw his chest suddenly heave a few times, and he quickly ran back into the house.

........

Note 1:

A comment yesterday said that Little Newton believes that light needs a medium, which led to the ether, which is indeed a misunderstanding on your part.

I didn't directly mention any water-bearing substances, what I was talking about were oceans, lakes, rivers, these macroscopic pathways, these are all refractive environments, if we want to discuss the inside of the medium, it should be water droplets or water molecules.....

Catching bugs is no problem, for example, in the previous chapter, a reader pointed out that L'Hopital's rule was proposed in 1696, what I actually wanted to say yesterday was a term in L'Hopital's rule, it was published in 1662, but the name was indeed a mistake in my expression, if it's wrong, it's wrong, I corrected it the first thing when I woke up.

But before you bring up some issues where you misunderstand and insist on your point, think about it carefully, it's meaningless to nitpick without considering the semantics.....