Light refraction through glass

[simpleman]

I'm a new poster ... I'm not that clued up on physics so I apologise in advance for the questions I will probably ask so I understand...

I'm intrigued by convoluted explanations that I've read concerning what seems to be a simple occurance.

Can someone please explain how beams of light shining through a pane of glass are refracted (ie, the angle of the beam coming out of the glass is not the same as that going in).

Ta,

[Epsilon=One]

Can someone please explain how beams of light shining through a pane of glass are refracted (ie, the angle of the beam coming out of the glass is not the same as that going in).Refraction is much more complex than you infer.

See Baskin's Physics Notes: Chapter 26, The Refraction of Light (http://www.valdosta.edu/~pbaskin/phys1112ch26notes.doc), for a start.

http://www.valdosta.edu/~pbaskin/phys1112ch26notes.doc

[simpleman]

Thanks for the link - have reviewed. This doesn't really explain how the refraction occurs, more how to calculate the magnitude of displacement etc...

It does raise more questions about this subject. I believed the speed of light to be constant. How then does it 'speed up' when emerging from a non-vaccum medium?

I'm just really interested in the medium of glass (ie, "transparent material with parallel sides).

Thanks for the reply so far...

[Epsilon=One]

Thanks for the link - have reviewed. This doesn't really explain how the refraction occurs, more how to calculate the magnitude of displacement etc...If it's the "Why?" of refraction that you want, you should begin with understanding the internal geometry of a light wave, bonds, and particles. I suspect a laureat would have problems with this. How advanced is your understanding of quantum mechanics?

I believed the speed of light to be constant. How then does it 'speed up' when emerging from a non-vaccum medium?The speed of light appears to be constant (non-accelerating); however that speed is dependent upon the "medium" (a poor word, I know) through which it travels. You must also think of light as a "wave front" curvature that has varying angles of intersection.

I'm just really interested in the medium of glass (ie, "transparent material with parallel sides).Your problem is complicated by the fact that there are parallel sides with different properties than the interior. Though, you are on to some of the complicating factors.

My best advice is to follow your interests. With such an inquiring mind, the search for answers should bring much wisdom.

[simpleman]

How advanced is your understanding of quantum mechanics?
It is about as good as any other of Schrodinger's cats.... Understand your point - I would never have imagined something seemingly simple to be so complex...

You must also think of light as a "wave front" curvature that has varying angles of intersection.
This is the whole 'is it a wave or is it a beam' discussion... If I'm assuming it is a beam (since I've read somewhere in which photon's were mentioned) that I could assume it was a beam and therefore ignore the whole 'wave' discussion / complexity - maybe I'm being naive...

Further, the angles of intersection still dont really tell me the 'how' it happens...

[Epsilon=One]

This is the whole 'is it a wave or is it a beam' discussion... If I'm assuming it is a beam (since I've read somewhere in which photon's were mentioned) that I could assume it was a beam and therefore ignore the whole 'wave' discussion / complexity - maybe I'm being naive...Depends upon the depth of understanding and accuracy of measurement that you are after.

Further, the angles of intersection still dont really tell me the 'how' it happens...I suspect you are after the "Why?" rather than the "How?"; if such is the case see my first comment in post #4, above.

[Radam17]

It's simpler than it seems after all that discussion.

First off, ignore the fact that the light could be a beam of photons. It will make it easier to understand the concept if you just treat it as a wave. Later, when you know more about quantum mechanics, you can worry about the wave-particle duality.

A basic property of waves is that the velocity of a wave (i.e. the speed of light) is constant for a given medium. However, the same wave will have two different velocities in the two different media. This is because the velocity(v) of a wave is dependent on two things, the wavelength(w) and frequency(f) of that wave (v=f*w).

As a wave passes into a new medium, there is a shift in it's wavelength due to the differences in the properties of the two materials. It is at the boundary between these two media that refraction occurs, as the velocity changes.

Since the frequency of the light is constant (or else it would change color as it passes into a new material, such as glass) the velocity has change in order to account for the difference in wavelength in order to maintain the relationship mentioned earlier.

From the relationship v=f*w, we can see that if the wavelength doubles, then the speed would need to be halved in order to maintain a constant frequency.

It is because of this change in speed that the light bends at the boundary of two media (refraction). When a ray of light passes into a medium in which is travels slower (a more optically dense medium; like from air into glass), it bends towards the normal (which is an imaginary line perpendicular to the pane of glass). When it passes into one where it travels faster (a less optically dense medium; like from glass to air), it will bend away from the normal.

Thus, when the light is in the glass, it travels at a different angle, but when it comes out of glass, it will come out at an angle near the same as the angle it went in. If you look through a normal pane of glass, like a window, you'll see very little displacement of the objects.

You can look up the formulas and such if you want to do some exact calculations, but that's the general concept as I understand it. Hope it helps.

[Epsilon=One]

It's simpler than it seems after all that discussion.Thanks for all the effort. Your explanation is straightforward and easily understood.

It appeared to me that "simpleman" may be delving deeper??

Your explanation is apropos for an engineer; I interpreted "simpleman"'s request more into the "Why?" of frequency, speed, and surfaces as well as medium.

I suspect refraction has much more to do with GR's light bending near massive bodies than Einstein's spacetime or gravitational attraction.

I'd be interested in your thoughts.

[airlinemusic]

Going through glass the angle changes.

Due to the old index of refraction.

The E vector is reflected at same angle.

The E and H light components behave differently.

Thats all I can recall and might be wrong now but must have got me
through class, if not convincing the teacher for some points.