# Why does the ray bend only in one direction?

By snell's law , the refracted ray bend away or towards the normal according to refractive index of the medium.

But it can be seen that the refracted ray bends to the right by an angle when a ray of light enters from left of the normal .

Why does not a ray of light bend to the same side as that of its incident ray when enters from one medium to another ?

• are you talkin about total internal reflection. also remember 100% refraction or reflection doesnt happen always. Related physics.stackexchange.com/questions/37731/… Commented Dec 27, 2014 at 14:33
• Not that. When we draw the incident ray from the normal to the media from the left side ( the angle of incidence is measured to the left fron the normal). The refracted ray always passes through the second medium taking an angle to the right from the normal drawn. Commented Dec 27, 2014 at 16:59
• actually if light travels from a rarer to denser medium it does "bend to same side as that of its incident ray" . if its denser to rarer its to right . Commented Dec 27, 2014 at 17:15
• Now let me explain more clearly to you. The refracted ray bends towards the critical angle in the right side. Not to the left side ? Commented Dec 28, 2014 at 2:56
• related Commented Dec 28, 2014 at 3:19

I think what you are asking is why a ray is refracted towards the normal when it passes into a medium of higher refractive index and why it refracts away from it when it passes into a medium of lower refractive index, i.e. and intuitive explanation of why light obeys Snells Law.

You can really only accept it if you accept that even a single photon is a wave that is not infinitely thin like a dimensionless particle (this would violate the uncertainty principle). What happens is when a ray hits an interface (change in index) one side of the wave changes phase velocity before the other side, resulting in a change in angle.

I think others have misunderstood your question, however it's an interesting one !

You are asking, why the refracted ray does not bend towards the same side of normal as of incident ray. Let's see, When we go from a rarer (u1) to denser medium (u2), the more denser the medium is the more the light bends towards the normal. What can be the maximum refractive index? When it tends to infinity

From snell's law

Sini/Sin r = u2/u1

As u2--> infinity it implies that sinr--> 0

Which implies that r-->0

Therefore the light cannot bend further and hence can not refract in the same side of incident ray !

Provided that the electron & the atomic beams also exhibit refraction,it seems that this is a particle's property.This is Newtonian explainable:you can see it if you are shooting the seewater with a machine gun.Also, if you are under water and shoot to the air with a fish gun.Simple vector analysis.Deflection angle is proportional to the friction (depending on particle's mass/size and the medium's density).Photon behaves as particle in this effect.Mass is given by de Broglie equation:m=hv/c^2 , v=frequency