I am a very conceptual kind of person and I'm trying to understand refraction, but after all my reading I'm still having some fundamental gaps that are preventing me from fully grasping it. (All of these questions are especially pertaining to how light waves refract.) Here's what I don't get: 1.) Snell's law states that the ratio of the sines of the angles of incidence and refraction is equivalent to the ratio of phase velocities in the two media. But what does it really mean to say that the sines of the angles of incidence are equivalent rather than the angles themselves as in the law of reflection? 2.) What is so important about the angle that a wave makes with the normal? If refraction is physically due to the wave's speed being slowed and it's wavelength shifting accordingly, then why is the degree of bending so dependent on the angle it makes with the normal? A light wave striking a piece of glass perpendicular to its surface, for example, will not be bent, it will go straight through, while a light wave striking that same piece of glass at an angle will not pass right through but will be bent first. What physically explains this, other than Snell's Law which just states it? 3.) Is there any physical explanation as to what causes a wave to bend toward or away from the normal depending on how its speed is changing? Thank you so much for the help!