# B Alternative to Double Slits

1. Jan 18, 2017

### mieral

Hello..

I'm writing a popularization book about quantum mechanics. I know most books start with ultraviolet catastrophe, Planck discovery of the constant.. and the double slit experiment. Is there other ways to start it without mentioning the double slit? Or is it essential to any laymen based quantum mechanics introduction book that there are just no other alternatives?

How about you. If you were to write a QM book for laymen and popularization. How would you start it and what ideas would you put first?

Thank you!

2. Jan 18, 2017

Young's double slit experiment was an important one, but the Bohr model of the atom to explain the atomic spectra with quantized angular momentum $L=mvr=n \hbar$ was also quite significant. Later on, the Zeeman effect with quantized spins that could be observed in a magnetic field was also of considerable significance. And don't forget the photoelectric effect for which I believe Einstein gave the explanation.

3. Jan 18, 2017

### mieral

Would it make sense to mention about the Stern-Gerlach experiment instead of the double slit experiment in a beginner's layman book? Or would it be too complicated that they would just not read the rest. What other books have you read that indeed mentioned the Stern-Gerlach instead of the double slit?

4. Jan 18, 2017

A google of the Stern-Gerlach experiment shows it also to be of much significance. (I had to google it because I had forgotten the details.) My preference is for spectroscopic experiments (with light), but perhaps that is because my background is largely in spectroscopy.

5. Jan 18, 2017

### mieral

My book would only have half of it reserved for quantum mechanics. So I can't include all this photoelectric, Zeeman, Bohr, Ultraviolet Catastrophe, etc. stuff. Would this work as a Laymen book? In Lisa Randall Warped Passages or Lee Smolin Trouble With Physics. They didn't include them too or so many chapters would be taken up. Are they supposed to be for Laymen?

6. Jan 19, 2017

### _PJ_

There's laymen and there's laymen. There's also an interest in selling books to people who are interested in the "story" rather than necessarily learning the "details".

Books like "How to teach QM to your dog" and John Gribbin's "Schrödinger's Cat"* use the Slit experiment to introduce and demonstrate the difference between a classical expectation and intuitive way of thinking and the reality of nature. Yet these are also replete with possibly misleading analogies and incomplete depictins. (no offense, I really love readig Gribbin's work, and I'm sure many young people have benefitted immensely with Chad Orzel's work as an introduction)

I too maybe considered a layman, since although I read physics and astronomy 20 years ago, unfortunately I was unable to complete the course and without a dedicated professor, it's very difficult to find adequate and reliable material to continue learning.

That's why I found Leonard Susskind (et al)'s Theoretical Minimum series to be invaluable and ideal for me, though arguably not for the more casual pop-physics readership. Notwithstanding the entire first volume introducing classical concepts and instilling the mentality of understanding physics in terms of states and energy - the second, and QM-sepcific book does not mention Young's experiment at all (if it does, it's only passing reference):

If it's helpful/relevant to you, the book does open and introduce the principle disparity between QM and classical concepts through the probabilistic notion of spin states and uncertainty -**

*Actally I think Gribbin (maybe pquoting Feynman) actually states something along the line of "Everything about QM can be found through the Double Slit experiment and its variations" - Which not only supports it as an ideal introductory piece but allows for continued referall and reinforcement of ideas as the book progresses to various aspects of quantum mechanics.
** Arguably given the point made just above, this could be entirely presented in terms of the Double-Slit experiment and momentum rather than angular momentum etc.

7. Jan 24, 2017

### Khashishi

The standard double slit experiment isn't so much a quantum mechanics experiment as a classical optics experiment. We've known about the wave behavior of electromagnetism long before quantum mechanics was understood. The double slit experiment becomes quantum mechanical when you start to decrease the intensity to the point where you can resolve individual photons hitting the screen, or when you use something like electrons as the interfering particle. So, the photoelectric effect is a more direct way of demonstrating the quantum behavior of light. We already knew that light was a wave, but the low intensity double slit experiment is important for demonstrating that light behaves both as a wave and particle. (Some authors state that light behaves as either a wave or a particle, but this is incorrect, and the low intensity double slit experiment shows that it is both simultaneously.)