# Schrodinger's Equation and Wave Function

So I understand that there exists the shrodinger's equation, which on solving,gives the wave function of an electron. The wave function as I understand, gives all possible information about an electron(any extra information on wavefunction will be appreciated).

Could someone actually solve a shrodinger's equation for an electron, and vaguely describe the process involved? Also after the wavefunction is obtained, could you explain to me what exactly does the wavefunction depict, and actually graph it?

I am having a lot of trouble grasping the concept. Any help will be greatly appreciated

• In a nutshell the Schrödinger equation gives the probability for finding an electron in 3D space around a nucleus. The nasty part is that it only works for a single electron. With two electrons you have a problem analogous to the three body problem of classical physics. – MaxW Feb 17 at 8:11
• @Max It is incorrect. The SE gives the wave function, which is more information than just the probability density. Also, IT "WORKS" for 2, 3 etc. electrons, too, only you cannot solve it analytically, which is a completely different story. – Greg Feb 17 at 8:23
• I am not sure that this site is the best resource for this question. The solution of the Schrodinger equation for a single electron in different potentials is generally a fairly standard part of any quantum mechanics or quantum chemistry course, however, it is rather long and needs university mathematics to get some idea of it. From start, it can be a half semester if you are not familiar with quantum mechanics. What we can briefly, but generally tell is something you most probably already have seen (eg. orbitals for H atom), or if you try to read it and have specific questions on details. – Greg Feb 17 at 8:29
• I would start by looking into the particle in a box, a common starting point in QM courses. See eg en.wikipedia.org/wiki/Particle_in_a_box – Buck Thorn Feb 17 at 9:19
• There is nothing special or unusual about this type of differential eqn. Standard maths techniques are used to solve it after we have defined the problem at hand, e.g. particle in a box or H atom etc. We interpret the square of the result of solving it $\psi^*\psi$ as the probability of finding the particle at a certain place. – porphyrin Feb 17 at 9:52

I suspect the problem is not mathematical. It is in the meaning of the wave function. Well. I will now show you how I explain it qualitatively in my high school classes. I state that the electron is like a violin string, but a string with three dimensions that is vibrating in the fourth dimension. As I know this last words are not understandable, I start with one dimension and pass slowly to two and three dimensions.

Let's start from a horizontal string whose end is fixed on a wall, and the other end is in your hand. If you put some energy to the string, it will vibrate in a stationary vibration. The string looks like half a sine curve, with the maximum in the middle of the curve. If you want to describe the curve with words and without drawings, you can say that the curve is like a half-sinusoid whose amplitude has the same sign all over its length, part time positive, part time negative.

Now if you put more energy in the string, it will vibrate in another mode, with a node in the middle. When one half of the string is vibrating upwards, the other half is vibrating downwards. With still more energy you can have it vibrate with two nodes. To describe the shape of the string as before without drawings, you can say that the string is a sinusoid with one or several nodes. So that you need one number $$n$$, the number of nodes, to describe its movement : $$n$$ is the first quantum number. $$n = 1$$ for the first vibration, because the only point not moving is the end of the string in the wall. $$n = 2$$ for the case with one node in the middle of the string.

Now let's consider the string in two dimensions. This is not a string any more, but a two-dimensional plate like a drum. If you hit it softly in the middle, it will vibrate with all its points moving simultaneously upwards then downwards. The only points of no vibrations are the periphery of the drum. In two dimensions, points of no vibration are replaced by lines of no vibration. Here there is only one such line : the number of nodal lines is $$n = 1$$.

If you put more energy by hitting the center of the plate, you may produce a new vibration mode if the center of the plate is moving upwards (or downwards) when the outer part is moving in the opposite direction. In this mode no vibration occurs on the small circle between these. This circle is a nodal line. There are two concentric circles on this mode. So $$n = 2$$. We may describe its amplitude by drawing curves of equal amplitude on the plate, like level curves on a map.

But it is going to be more difficult, because there is another type of vibration on the plate. If you hit the plate not in the center, but elsewhere, you may produce a plate vibration where one half of the plate moves upwards and one half downwards. Here the nodal line is a diameter. And there are two nodal lines : the diameter and the periphery. Here $$n = 2$$. As a consequence, two vibration modes exist with the same quantum number. We must introduce a second quantum number, which is called $$l$$, and which is the number of straight nodal lines. So this type of vibration is given by $$n = 2$$ and $$l = 1$$. Hopefully you understand that other vibration modes do exist with the drum, with arbitrary values of $$n$$ and $$l$$ < $$n$$

Let's summarize. An object with one dimension vibrates in another dimension, and one quantum number is enough to describe its vibration. An object with two dimensions is vibrating in the third dimension, and two quantum numbers are required to describe its vibration. The number of dimension is equal to the number of quantum numbers.

Now let's go to the electron, which has $$3$$ dimensions, and which may be considered as if vibrating in a fourth dimension, called $$\Psi$$. As this dimension cannot be represented in our world, all we can do is to give different numerical values to three quantum numbers for all vibrating modes, and represent surfaces which correspond to equal numerical values of the local "vibration" of the electron. These surfaces of equal value of $$\Psi$$ are spheres for $$l = 0$$, the famous dumb-bells with two lobes for $$l = 1$$, because of $$1$$ nodal plane. Here is how it goes.

Here is how I explain the wave function to my high school students. They usually have some difficulty understanding. But all have told me that this explanation had helped them sudying quantum mechanics later on in college.

• While this can have a value explaining why there is a need for numbers describing the vibrations of string and surface, it says absolutely nothing on the meaning of the Schrödinger function. – Alchimista Feb 17 at 17:38
• @Alchimista. It is right. It does not mention Schrödinger equation. it just explains the nature of the wave function. – Maurice Feb 17 at 18:14