# Light in a cup (Can you explain this phenomenon?)

Tags:
1. Jun 9, 2017

### Anshul23

Can anyone explain the behavior of light I came across as I sat in my lounge this evening having a nice cup of Mocha . Hint ( I am sitting in a room with some led ceiling lights on) can you:
1.Guess how many Led lights I have on
2.Explain the appearance of light which is looking like a typical double volcano lol.
3. Do try to express the situation in terms of elaborate equations.

Last edited by a moderator: Jun 9, 2017
2. Jun 9, 2017

3. Jun 9, 2017

### Anshul23

Damn! this fast. I thought of tachyons for a moment :D But still how many sources of light

4. Jun 9, 2017

### OmCheeto

Looks like two to me.

5. Jun 9, 2017

### Drakkith

Staff Emeritus
Each "volcano" is the result of massive spherical aberration of the focused light. The coffee cup is circular in shape and focuses the light similar to a spherical mirror, except only in one dimension. See the diagram of the concave mirror in this article: https://en.wikipedia.org/wiki/Spherical_aberration

6. Jun 9, 2017

### Janus

Staff Emeritus
Here's a quick render of light reflected from the inner side of a semi-circle. You can get some really pretty patterns just by reflecting light off of curved surfaces

7. Jun 10, 2017

### Anshul23

Correct

8. Jun 13, 2017

### mister mishka

Yeah it is caustic optics, I play around a lot with this for some of the visual films I create. Check out the film below, I use various reflective materials behind a warped piece of glass, shining various lights and lasers at it from different angles, filmed out of focus to amplify the textures of light..

https://vimeo.com/mistermishka/space008

9. Jun 13, 2017

### Anshul23

Thats a great video BTW

10. Jun 14, 2017

### mister mishka

Thanks!

Yeah I have lot more interesting stuff already filmed, but am working on releasing them this fall with music mixes (9 hours of my best stuff, from my 55 hours of footage). However, I will also be making a small selection of content solely for PhysicsForums review, because of the interesting science behind some of my films that I think people here would like. Also since I have used these forums a lot to actually get an understanding of what is actually happening with certain experimental filming techniques I've found out (things like polarizing light, diffraction, fractals, etc).