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Name: Anthony
Status: student
Grade: 9-12
Location: MD
Country: USA
Date: Winter 2012-2013

I understand how refraction is calculated when light hits a surface (and all the other details about critical angle and total reflection, etc). My question is: Hypothetically what happens when light hits a corner (of say the corner of a perfect cube)? Does it refract, reflect, scatter the light in random directions, or just enter the object, or something else? The reason why this case is different from light hitting any ordinary surface is that there is no real surface that the light encounters. Instead, it hits a corner (i.e. a point).

When light ( or any electromagnetic radiation and even atoms/molecules) encounters the edge of a cube that is an order of magnitude of the impinging radiation it interacts by diffraction. The details are too mathematically messy to explain here, but the following web site treats diffraction well and in detail:

Vince Calder

Hi Anthony,

Thanks for the question. The questions is hypothetical since one cannot exactly hit the corner of the cube (or any other object for that manner.) Generally, when light hits a surface, there will be a combination of reflection and refraction. The amounts of reflection and refraction depend on the indices of refraction. Reflection can be divided up into two types: specular and diffuse. Specular reflection is reflection from a really flat surface. Diffuse reflectance is reflection from a rough surface and the light "diffuses" or spreads out in random directions.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell

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