# What is Caustic: Definition and 12 Discussions

In optics, a caustic or caustic network is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light. Therefore, in the photo to the right, caustics can be seen as patches of light or their bright edges. These shapes often have cusp singularities.

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1. ### MHB Difference between caustic soda and caustic potash

I read the chemical formula for Potassium Hydroxide (Caustic soda)=NaOH (1)I also read the chemical formula for caustic potash having same chemical name Potassium Hydroxide =KOH. I want to know what is the difference between these two chemical compounds in terms atoms, molecules, ions? Why...
2. ### Is caustic surface of an astrophysical black hole one event?

MTW, p. 924, defines a caustic as a point where a null geodesic originating from the external universe enters a black hole's event horizon, remaining in the horizon afterward for some finite affine interval. (A null geodesic of this type is called a generator of the horizon.) They introduce this...
3. ### Calculating 1/4 Earth Arc with Trig

Is there a way to determine the arc around 1/4 of the Earth without measuring it? I mean like thru trig?
4. ### Residue on steel after caustic cleaning

After cleaning aluminum from steel I use with sodium hydroxide, there a brown chalky layer I want to clean off. Other than sanding, I cannot remove it. Is there a way to chemically remove it without affecting the steel?
5. ### Caustics/Cusps Software Search

Hello folks, I'm looking for a free programme to play with caustics/cusps. Does anyone know where I can find one? If not does anyone have any suggestions as to how to write a script for one in gfortran? Preferably all I'm after is a way to make quick plots of cusps in 2D. Cheers and thanks a...
6. ### A Material that Can Withstand High Pressure & Caustic Condition

I am interested in locating a material that can withstand a strong alkaline medium (10 M KOH) and approx. 5 atm pressure... I am somewhat new to material chemistry so all I have been able to think of thus far is PVC pipe. Through my research I have discovered that PVC is highly fire retardant...
7. ### Optics -- caustic curve equation

I went through this article: http://users.df.uba.ar/sgil/physics_paper_doc/papers_phys/ondas_optics/caustica1.pdf But I think that when we do F=0, we are assuming the centre of the curve to be the origin and assuming the curve to be a circle, because only then will we be able to say that OP=ON...
8. ### Converging wave interference generating a caustic

Dear reader, I have written a paper which I require a reference for converging wave interference generating a caustic. When studying for my degree, I performed Young's double slit experiment with the addiction of a converging lens. I was trying to comprehend Afshar's...
9. ### Caustic curves and dual curves

Hello, I'm investigating duality for plane curves, and I came across an 'original' interpretation of the Biduality theorem , that uses the notion of caustic curve. Because everything is still very obscure to me, I try to share the whole with you, in the hope that we can help to fix ideas...
10. ### DimSum Restaurant's Secret Ingredient: Caustic Soda?

'tother day I chanced to look in the back room of a local DimSum restaurant and saw bags and bags and bags of caustic soda - like a skid of it. What use would a restaurant have for hundreds of pounds of caustic soda? I looked it up on Wiki and found only two uses that make sense: - washing...
11. ### Caustic curve - shadow in the cup

Hello, I need help... I have been assigned in physics to look at the shadow in the cup and mysearch shows me caustic curves... I have very little information on this to do a 4 page report on... can someone please point me to some sites, url etc on this... many thanks
12. ### The Skin's Natural Protection Against Caustic Chemicals

I didn't know where to put this since it pertains to both chemistry and biology so i put it here. One time i accedently spilt 31.45% concentrated HCl on my skin and didn't notice it right away but then i saw this fuming drop on my skin and i immediately washed it off, it never tingled, burned...