1. Dec 2, 2009

### raisin_raisin

I have a light source emitting near a surface and then getting refracted. I have calculated the solid angle leaving the surface of the light I am interested in but need to find what cone this corresponds to from the emitter. Can I just stick half the solid angle into Snell's law equation even though the solid angle is in steradians and then use this answer (which presumably is in radians) as my new solid angle?

Thank you for reading, I hope I have explained what I mean (i.e basically can I use steradians in Snell's law)

2. Dec 2, 2009

### mgb_phys

If the beam is symetric then yes you can just use the cone angle with snell's law then work out the new solid angle from the new cone angle.

If the cone angle is large you might have to take more care since the different edges will be refracted different amounts and you wont have a symetric cone on the output

3. Dec 2, 2009

### raisin_raisin

Thank you very much!

4. Dec 2, 2009

### Redbelly98

Staff Emeritus
Uh, but you cannot just use the steradians value as the angle for Snell's Law. You do have to figure out how many radians the half-angle of the cone is.