# Can light reflect light

I want to ask that in vacuum or any other medium can light reflect itself ? I an asking for visible light in the spectrum but of any other light does so please answer .

• Where have you looked yourself, there are almost certainly duplicates of your question on this site? – user140606 Jan 16 '17 at 13:56
• They were about electrons reflecting light and I had this question in mind so I asked it. – Abhinav Dhawan Jan 16 '17 at 15:24
• This can occur classically in non-linear media and quantum mechanically in vacuum, see here. – gj255 Jan 16 '17 at 16:04

Can light reflect light ... I [am] asking for visible light

No, light waves pass straight through other light waves. This is one of the first things you are taught about light in any school-level physics course.

The fact that two waves continue on their way when they have passed through each other as if there had never been an encounter will come as no surprise to students who have:

• closely observed raindrops falling in a puddle, or
• thought about the fact that signal-carrying microwaves and radio waves pass through each other constantly, particularly in cities dense with communications.

Still it is remarkable.

## Corner cases

Physics being what it is, there are some ideas that can serve to confuse ...

### Photon-Photon scattering

a new analysis in Physical Review Letters shows that the Large Hadron Collider (LHC) at CERN could detect around 20 photon-photon events per year.

The question asks about "visible light", so that would be light of the sort directly visible to humans.

20 events a year is pretty few and I imagine the conditions in the LHC, when operating, are pretty far from the sort of conditions living humans should place their eyeballs into.

### Pair production

To create an electron-positron pair, the total energy of the photons must be at least $2m_ec^2$ = 2 × 0.511 MeV = 1.022 MeV (me is the mass of one electron and c is the speed of light in vacuum), an energy value that corresponds to soft gamma ray photons.

AFAIK visible light doesn't include soft gamma rays.

• So the light would not interact with other light even as particle (photon) ? – Abhinav Dhawan Jan 16 '17 at 15:38
• Generally, the wave model is useful when light is not interacting with matter. The photon model is more useful when light is interacting with matter. Therefore the photon model is not useful when considering how light interacts with light. – RedGrittyBrick Jan 16 '17 at 15:40
• Still, there's 1) concept of geon, 2) photon-photon scattering. – Ruslan Jan 16 '17 at 15:58
• High energy light waves can collide, interact and create pair production. Whether that counts as reflection might be open to interpretation. en.wikipedia.org/wiki/Matter_creation – userLTK Jan 16 '17 at 16:04
• Answer updated for corner cases not normally associated with visible light in ordinary life. – RedGrittyBrick Jan 16 '17 at 16:29