3k views

### Do photons actually slow down in a medium, or is the speed decrease just apparent? [duplicate]

Some places I've read flat out say light actually slows down in a medium, some say the speed decresae is just apparent but not real and that the photons still travel at the constant speed of light. I'...
43k 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 ...
2k views

### Why is the speed of light said to be constant when we know it slows down in a medium? [duplicate]

If we ask someone what the speed of light is, they will say that it is constant and its value is $3\times 10^{8}\ \mathrm{m/s}$. But if we recall refraction of light, we say that when the light ...
12k views

### What causes refraction of visible light? [duplicate]

Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light ray toward the ...
359 views

### Why does the speed of light change? [duplicate]

While researching the cause of refraction, I found that refraction occurs due to the change of speed of light when it goes from one medium to another (according to Huygens principle). But I cannot ...
2k views

### Does the speed of light vary depending on what it travels through? [duplicate]

The title is pretty much self explanatory. Does the speed of light vary depending on what it is traveling through? The speed of light through vacuum is 299792458 meters per second but does it change ...
1k views

### What causes refraction of light? [duplicate]

Time and again, I've been told that the change in the velocity of light makes it bend at the interface between two different media. But is there any explanation as to why that change occurs? Or is it ...
580 views

### How is light slowing down in a medium thought of in the photon picture? [duplicate]

The speed of light in any medium besides vacuum is smaller than $c$. In a classical way, I just look at that as a wave that propagates less fast, the change in EM-field is passed on slower. How should ...
512 views

### What happens to light as it passes through a medium? [duplicate]

Light travels at its maximum speed in a vacuum. But when it enters a medium such as glass, air, water, etc. it slows down. What is actually happening to the photons as they pass through the medium? ...
441 views

### Does light really slow down when moving through a transparent medium? [duplicate]

I assume its speed doesn't change but the photons get absorbed and destructed by the materials' atoms and then they emit new photons. Is that true?
185 views

### Is the speed of photon always $c_0$? [duplicate]

The propagation of light in medium is sometimes interpreted as the photons moving with $c_0$ (the speed of light in vacuum), occasionally absorbed by particles and released again by transition, ...
103 views

### Do the mediums decrease or increase the speed of light? (source to target) [duplicate]

If sun is the source of light then is it possible that the speed of light might increase depending on the mediums its going through or its not possible.
110 views

### Change in Speed of Light [duplicate]

Whenever light enters from air to glass its speed decreases but when it cross the glass and again come in air its speed increases. What is the reason behind this property? What is slowing it and what ...