# All Questions

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### Electron and photon collision

So electron moving left ($v_{initial}=0.8c$) collides into photon going right. After the collision electron is moving to right ($v_{after}=0.6c$) and the photon is moving to left. What is the ...
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### Do photons feel gravity of approaching objects only?

I have read that photons while travelling near massive objects such as the sun experience gravitational pull which is why we see some stars at different positions than they are when seen towards the ...
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### What would give us more heat ? infrared or microwaves?

As we know that our body is made up mostly of water and the frequency of vibration of water molecules matches that of microwaves which is the working principle of microwave ovens. When we come in ...
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### Is Lagrangian a scalar?

I may be wrong: Lagrangian are scalars. They are NOT invariant under coordinate transformations. The simplest example is when you have a gravitational potential ($V=mgz$) and you translate $z$ by $a$ ...
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### Higgs field in space around us?

Is the higgs field in space around us? I understand it as that the higgs field has a constant value on every space time point, is that right? And this value is the vacuum expectation value. This ...
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### Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
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### Can there exist a Wave which changes the quantum states of particles?

i'm a high school student and i was reading about electromagnetic waves and how they transport energy and that the electric and magnetic fields sustain each other. I have also read about longitudinal ...
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### Does an object slow down after acquiring terminal velocity?

Once an object reaches terminal velocity in free fall, is there a point in time when the object actually starts slowing down due to resistance, or does it stay constant?
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### Flammability and statistical mechanics

I am wondering to what extent the flammability can be predicted from the statistical properties of an ensemble. Given the partition function of an ensemble, can we in principle predict this property? ...
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### Ж (“zhe”) in string theory?

I was just recently watching a TED talk about string theory, by Thad Roberts, and at around 11:10 into the video he mentions a constant for maximum spacial curvature called "zhe" (the Cyrillic symbol ...
756 views

### Why doesn't the magnetic field of a coil “cancel out”?

In a coil, we can see that the current moves right, then left, then right, then left, and so on as it travels down the coil. According to the right-hand grip rule, isn't the magnetic field going in ...
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### How to choose Gaussian surfaces while solving problems?

I have a doubt regarding this problem: Two large identical flat metal plates are placed parallel to one another, seperated by a small distance compared to their linear size. One plate is given a ...
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### Clock synchronization and dilation

This is a question on the synchronization of clocks. If a girl on a train has the same clock that a guy has on the platform and they synchronize their clocks at 12am together when the train and the ...
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### Alternative Critical Dimensions in String Theory

Is it possible to write down a Lagrangian for a string theory with a critical dimension different than the familiar 10 or 26? How could one find a string theory Lagrangian for a given dimension? Could ...
1k views

### Potential energy curve for intermolecular distance

I'm trying to understand this curve better, but I can't quite figure out what "negative potential energy" means. The graph should describe a molecule oscillating between $A$ and $B$, however where I'...
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### Different kinds of the same isotope

I apologize if this is an obvious question, but I can't find the answer anywhere. In this page: http://ie.lbl.gov/education/parent/U_iso.htm are listed the isotopes of Uranium. Some of them, for ...
551 views

### What actually happens at the microscopic level in a Zener diode in reverse bias?

A Zener diode is used as a voltage stabilizer. The graph of current vs voltage of Zener diode clearly shows that there is a constant voltage across Zener after the breakdown voltage as the current ...
14k views

### Why do shadows from the sun join each other when near enough?

I was laying on my bed, reading a book when the sun shone through the windows on my left. I happened to look at the wall on my right and noticed this very strange effect. The shadow of my elbow, when ...
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### What is the current physical theory of what causes the 'Morning Glory' roll cloud over Northern Australia?

The Morning Glory roll cloud (pictured below): from this Wikipedia page, which briefly describes the landform and meteorological causes, but states The Morning Glory cloud is not clearly ...