# Tag Info

### Do black holes emit no light or does light fall back in black holes?

If a luminous object falls into a black hole, that object will continue to emit light as it does so (for some finite time measured on its own clock), even if it is inside the event horizon. That light ...

### Do black holes emit no light or does light fall back in black holes?

Let us conduct a following experiment: We send a photon to a mirror hovering near the event horizon of a black hole, and we observe what happens when we move the mirror closer to the event horizon. We ...
1 vote

### Do black holes emit no light or does light fall back in black holes?

Your intuition is that of Newtonian mechanics, I can say this because you said "Black holes have such a strong gravity that escape velocity from it is more than speed of light which basically ...

### Do black holes emit no light or does light fall back in black holes?

No. Light does not escape up to any point. It isn't the case that light goes to some distance away from, say, an $r$ slice if we emitted from a constant $r$ surface inside a Schwarzschild black hole ...

### How to calculate a straight edge diffraction pattern?

The discussion so far has stated that the x value of the first order fringe is 6.1E-04 when L-D is infinite, D =1 m, lambda is 5E-07 and 0.75 is added to m. The subsidiary question is whether there is ...

### Shooting a single photon through a double slit

An old post I know but this is the best answer I have found after an hour of searching. So it is impossible to fire a single particle toward a slit with accuracy (but the slits have to be very close ...

### Deriving the Coulomb force equation from the idea of virtual photon exchange?

I've gone through the same thought process as you, so I suspect the question you're really trying to answer is: "Can the formula for the electric Coulomb potential be generated as a natural ...

### How can radiation be a transverse wave? Does light really resemble a rope? How can a 3D field be a medium for non-spatial 1D waves? Need mental model

EM waves are produced when atoms are made to move more quickly. Heat can do this. When EM waves are emitted from the excited atoms, the EM waves propagate in all directions of a compass (shape of a ...
1 vote

### Equation-of-state for a photon gas

Under some conditions, radiation can be modelled as a fluid with a proper equation of state. The idea is that the photon gas should be close to equilibrium with a second fluid (matter), making the ...

### Intensity of light and energy at a photonic level

If I understand correctly, the intensity of light is proportional to the number of photons hitting a certain area. The intensity of light is proportional to the number of photons and their energy ...

### Intensity of light and energy at a photonic level

Photons are quantized excitations of the electromagnetic field. The physical properties of a photon are encoded in the possible eigenvalues of the observables expressed in terms of the associated ...

### How does the Hong-Ou-Mandel (HOM) effect conserve photon momentum?

The only easy way to see generic momentum conservation in quantum experiments is to not look at just one possible outcome, but rather to look at expectation values (weighted averages, over all ...

### Visualization of a Photon

The first thing we need to understand is that quantum mechanics is a formalism. In other words, it is a mathematical language in terms of which we model the physical world. There is a difference ...

### Photon emission rate frequency dependency

In theory, assuming the mechanical displacement of the charged particle is fixed, yes. I am, however, finding it hard to think of a real radiation process where the mechanical displacement is ...

### Density of photons in an expanding image?

What if the source is a candle? Is the original source always sufficient to 'map' adequate photons to any sphere that may be created in the dimensions of our universe? The chemical process of ...

### Density of photons in an expanding image?

If you consider light as individual photons radiating spherically from a point source then technically at any radius beyond the origin there would be gaps. The energy is quantized because it's ...

### Density of photons in an expanding image?

How much must the sphere expand so that there are gaps in the image when sampled at different locations on the 'instant-sphere' image? The photons (at least prior to detection), don't have a specific ...

### What happens when a photon "dies"?

I feel that dark matter is but burned-out decayed light; no energy and no mass but has volume and somehow has weight and structure, so not normal stuff. As suns discharge light all the mass and energy ...

### Graphical depiction of one photon

What you've described is a classical electro-magnetic wave with a certain frequency. To figure out how photons relate to this, you'll need to quantize the field, and deal with Fock states. Fock ...
1 vote

### Number of incident photons

You've provided enough information. Assuming every photon emitted is of the same wavelength, we can use the following equations. First, to related power and intensity: $$I = \frac{P}{4πr²}$$ I for ...
1 vote

### How to understand the Orbital angular momentum of a photon that is not an integer？

As a starting point, topological charges associated with light have integer values as they represent the "holes" in the topology describing the phase space of the light. In this regard they ...
Accepted

### One-way photon detector

This statement holds for all devices that are reciprocal, or time reversal invariant, One Way Mirrors do not exist. Thus your detector doesn't exist. However, let's look at 2 situations where you ...

### Why don't photons align in an electric/magnetic field?

Both an electric and magnetic field do indeed cause a rotation of the electro-magnetic alignment of photons. The magnetic influence was already described by Faraday in 1845. The electric influence is ...

### Are there practical applications for boson sampling?

Boson sampling is a famous "useless" problem but in fact there are a couple areas of practical applications. One is for Proof-of-Work consensus, wherein a network of adversarial players ...
1 vote

### Which is the lightest thing in this universe? Is that a photon or neutrino?

Photons are massless particles, while neutrinos have a tiny but non-zero mass.