# All Questions

482 views

### How to define the order parameter of the q-state Potts model?

The order parameter of Ising model can be defined as $m=\frac{N_1-N_2}{N}$, if $N$ is the total number of lattice points, $N_1$ and $N_2$ is the number of lattice points spin up and down respectively, ...
181 views

### Potential step solution is not normalizable

If you try to integrate the solution of the potential step, http://en.wikipedia.org/wiki/Solution_of_Schr%C3%B6dinger_equation_for_a_step_potential#Solution you will notice that it diverges! Doesn't ...
2k views

### Why is Entropy expressed in terms of Enthalpy?

Why does ${\Delta}S_{m(fusion)} = \frac{{\Delta}H_{m(fusion)}}{T}$ ? I always thought ${\Delta}S = \frac{dQ}{T}$ In this case does it mean $dQ = {\Delta}H$ ?? Why is it so?
284 views

### Total positive charge in the Universe

In their last homework, some of my students miscalculated a charge to be $10^{20}$ C over a squared meter and I was wondering if there was as much positive charges in the entire Universe. It would do ...
1k views

### Accelerating an elevator

A person is standing on a weighing scale in an elevator in upward acceleration. Let $N$ be normal reaction force exerted by the weighing scale to the person (upward). It is known that the person ...
89 views

### How does a photon leave trace of its polarization state in a photon detector but not trace of which direction it came in?

Some quantum erasure experiments involve polarization of photons. In one such experiment with a double slit, a horizontal polarizer is used in front of one slit, and a vertical polarizer is used for ...
314 views

### double slit experiment with two opposite quarter waveplates

Consider the usual double slit experiment involving laser and a double slit and a screen. Now place in front of the left slit a quarter waveplate (let's call it QWP1) that changes a certain linear ...
918 views

### Demonstrating Quantum effects with home experiments using green diode laser [closed]

I would like to preform home experiments to demonstrate quantum effects to my kids. I need a list of experiments on Laser photons that could be easily conducted at home to demonstrate quantum ...
5k views

### Magnifying Glass-How does it work? [duplicate]

How does a magnifying glass work? I know it creates a virtual image of the observed object but how is it possible that humans can see the virtual image?
373 views

### Spinning liquid to create a centrifuge effect

I'm in the business of purifying used cooking oil. Normally, I heat the oil up and let it settle for a couple of days. Water and solids settle to the bottom and cleaner oil remains on top. I'm trying ...