Abeam of light is traveling inside a solid glass cube having index of refraction 1.53. it strikes the surface of the cube from the inside. (a) if the cube is in air, at what minimum angle with the normal inside the glass will this light not enter the air at this surface? (b) what would be the minimum angle in part (a) if the cube were immersed in water?

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.