# Photons are produced at random?

• Chaos' lil bro Order
In summary, the conversation discusses the direction of emitted photons from a hydrogen atom after being struck by a photon at a random angle. It is possible for the emitted photon to have a correlation with the direction of the incident photon, which is known as a coherent process, or for it to be random, known as an incoherent process. The concept of conservation of momentum is brought up to explain this phenomenon. The conversation also touches on how this relates to absorption spectra and whether certain absorption lines are prohibited due to this mechanism.
Chaos' lil bro Order
Consider a hydrogen atom. A photon strikes it at some random angle. The hyrogen's electron absorbs the photon. The electron becomes excited and its orbital increases. The electron deexcites and emits a photon.

Question: Is the direction of the emitted photon a random direction. Or is there a correlation with the emitted photon's direction with the original incident photon's direction?

Chaos' lil bro Order said:
Is the direction of the emitted photon a random direction?
You can answer your own question if you consider conservation of momentum. (A photon of energy E has momentum |p| = E/c.)

Chaos' lil bro Order said:
Question: Is the direction of the emitted photon a random direction. Or is there a correlation with the emitted photon's direction with the original incident photon's direction?

Both can occur. It if there is a correlation, we talk about a coherent process, if not, we talk about an incoherent process. Usually the "absorption-re-emission" process is incoherent.

DrGreg said:
You can answer your own question if you consider conservation of momentum.

That seemed reasonable at first (I can see through water), but then I started thinking about absorption spectra. If I hit a sample with photons of an appropriate energy to excite the atoms, and assume the atom will emit the exact same frequency, then obviously in the atom's rest frame it cannot have altered the photon's direction. But without scattering, I shouldn't be able to measure absorption spectra.

Is this actually a mechanism that prohibits certain absorption lines, or was my assumption wrong?

## 1. What are photons?

Photons are elementary particles that make up light. They have no mass, but they have energy and momentum.

## 2. How are photons produced?

Photons are produced when an atom or molecule moves from a higher energy state to a lower energy state. This process is called emission.

## 3. What does it mean for photons to be produced at random?

When we say that photons are produced at random, it means that they are emitted in an unpredictable manner. We cannot determine when or where a specific photon will be produced.

## 4. What is the significance of photons being produced at random?

This random production of photons is essential for many processes, such as photosynthesis and the functioning of electronic devices. It also allows for the phenomenon of quantum entanglement.

## 5. Can we control the production of photons?

While we cannot control the production of individual photons, we can manipulate the conditions that lead to their production. For example, we can control the energy levels of atoms or molecules to produce specific wavelengths of light.

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