0
votes
2answers
67 views

Why does the light travel slower in denser medium? [duplicate]

Wikipedia says that "in general, the refractive index of a glass increases with its density." And the refraction index of water vapor is less than ice, and even less than liquid water. Is there any ...
1
vote
1answer
81 views

Does the light speed change in media? [duplicate]

Does the light speed change? The Theory of Relativity says that the speed of light in vacuum is the same and unchangeable, while I read that the speed of light in glass is lower than in air, and that ...
2
votes
1answer
49 views

Where / what is the source of the force that causes refraction?

So we know that as light moves from, say, a glass block to air, it speeds up and refracts, but if there is to be acceleration then surely there must be a resultant force to cause it? So where does ...
1
vote
2answers
48 views

Does the speed of light in different mediums affect the lorentz transformation?

We know that the Lorentz transformation is derived using the speed of light in vacuum. But if we were to use it in water, would it change since the speed of light in water should also remain constant ...
3
votes
1answer
134 views

Is there a way to increase the speed of light itself?

When light enters materials it slows down due to its refractive index (due to absorbing and re-emission of photons). But, is there a way to increase the speed of light itself? Can there be some ...
0
votes
3answers
127 views

Is light slower when traveling inside a gravity field?

This question is not about phase velocity changed which causes refraction, but about the real time itself being slower by the gravity of any object (from general relativity). If so, would this mean ...
-2
votes
4answers
239 views

Why is the speed of light considered as a fundamental constant if its speed changes with medium resulting in refraction? [duplicate]

I know that the speed of light, the universal constant of gravitation and the Planck's constant are considered to be the three fundamental constants of the universe. But, why is speed of light ...
2
votes
1answer
148 views

Faster than light in plasma

Some plasmas have a refraction index of less than 1. In these plasmas the phase velocity of light can be faster than light-speed. But the phase itself won't transfer information, so no paradox occurs ...
2
votes
3answers
430 views

Two different mediums can have equal index of refraction?

In other words: given a certain medium, is light's phase velocity unique?
1
vote
1answer
192 views

Simple Question: Speed of Electromagnetic Waves in a Medium

If the speed of an electromagnetic wave in a particular medium is such that $v = c$, the speed of light, does this mean that the permeability $\mu = \mu_0$, i.e. that of a vacuum and the index of ...
2
votes
1answer
90 views

Relation of color and frequency for the visible spectrum

In this question the OP is looking for a way to see light that is outside of the visible spectrum without using electronic sensors. This got me wondering about the visible spectrum itself. Typically ...
1
vote
2answers
374 views

Why does light not refract when incidented perpendicularly?

I had read that light does slow down in glass because photons interact with atoms in glass. They are absorbed and re-emitted and during this phenomenon it's speed decreases. See also this and this ...
1
vote
0answers
19 views

Speed of Light in a Medium [duplicate]

For light travelling in a medium with refractive index greater than one: The "average" speed of light is slower than the speed of light in a vacuum. As far as I know, the instantaneous speed of light ...
1
vote
2answers
262 views

Refractive index inside a fibre

The refractive index $n$ of a fibre is calculated as; $$ n = c_0/c_m $$ Where $c_0\approx 300000km/s$ is the speed of light in a vacuum, and $c_m$ is the speed of light in the fibre in question. How ...
2
votes
3answers
332 views

Difference in velocity of light in change in medium [duplicate]

It is often seen that according to physics the light changes it's velocity according to the medium through which it is traveling. So can it be explained that why so happen?
1
vote
1answer
214 views

Speed of light and virtual particles

After becoming extremely bored while studying for an Afrikaans exam, I started thinking about virtual particles. So, can light (photons) interact with virtual particles (even though they only exist ...
0
votes
1answer
118 views

Is the acceleration and deceleration of a wave instantanious?

When an light travels in free space, it has a velocity of propagation equal to the speed of light. However, then the light enters a medium with a refractive index of n, the velocity of propagation ...
-7
votes
1answer
314 views

Speed of light is not fixed? [closed]

In my research, I found that the speed of light is not fixed. IS it true? Namely, We know that light refracts when the medium it travels through changes. Actually, light travels in the same medium ...
3
votes
1answer
256 views

Fermat principle: which index of refraction?

I am somewhat puzzled by a common formulation of the Fermat principle (light travel time), because it contains index of refraction related to phase velocity while light travel time through a slab of ...
1
vote
2answers
58 views

Does the efficiency of radiation change in any way in the presence of a medium?

I've read that radiation doesn't really require a medium. But if you're taking, for example, the sun's light, then does its efficiency of transmission increase or decrease once it reaches the earth's ...
5
votes
2answers
31k views

Why does wavelength change as light enters a different medium?

When light waves enter a medium of higher refractive index than the previous, why is it that: Its wavelength decreases? The frequency of it has to stay the same?
2
votes
6answers
2k views

Do photons have acceleration?

Photons travels with the largest speed in our universe, the speed of light. Do photons have acceleration?
1
vote
1answer
694 views

What do physicists mean when they say “speed of light”?

Does it make sense to say, "The speed of light varies?" Some may say right off the bat "Yes, it changes as a wave passes through a different medium." However, I'd like to say no, because when I hear ...
17
votes
3answers
2k views

What really cause light/photons to appear slower in media?

I know that if we solve the maxwell equation, we will end up with the phase velocity of light is related to the permeability and the permittivity of the material. But this is not what I'm interested ...
12
votes
3answers
717 views

Can the speed of light become complex inside a metamaterial?

The speed of light in a material is defined as $c = \frac{1}{\sqrt{\epsilon \mu}}$. There are metamaterials with negative permittivity $\epsilon < 0$ and permeability $\mu < 0$ at the same time. ...
19
votes
4answers
1k views

What is the mechanism behind the slowdown of light/photons in a transparent medium?

So light travels slower in glass (for example) than in a vacuum. What causes light to slow down? Or: How does it slow down? If light passes through the medium, is it not essentially traveling in the ...