Why Does the Speed of Light Change in Different Mediums?

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SUMMARY

The speed of light in a vacuum is a constant at approximately 3 x 108 m/s, but it decreases when passing through different mediums due to the medium's refractive index (n). The refractive index is defined as n = c/v, where v is the speed of light in the medium. As light enters a denser medium, its speed and wavelength decrease while its frequency remains unchanged, leading to phenomena such as refraction. The absorption and re-emission of light particles in a medium contribute to this change in speed, creating a complex interaction that differs from the behavior of light in a vacuum.

PREREQUISITES
  • Understanding of the concept of refractive index (n)
  • Familiarity with the wave equation: v = frequency x wavelength
  • Basic knowledge of light behavior in different mediums
  • Awareness of the distinction between vacuum and other mediums
NEXT STEPS
  • Research the principles of light refraction and Snell's Law
  • Explore the concept of electromagnetic waves and their properties
  • Study the absorption and emission processes of light in various materials
  • Investigate the implications of the speed of light in quantum mechanics
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Students and professionals in physics, optical engineers, and anyone interested in the fundamental properties of light and its behavior in different environments.

quantizedzeus
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Speed of light...

It makes no sense to me that if the speed of light is always c...then in different mediums why this speed changes...?? I may have got it in a wrong way...But can anyone help me out in detail...(thanks)
 
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The speed of light in a vacuum is always c.
 


Does it puzzle you that the speed of sound is different in air than in water?
 


quantizedzeus said:
It makes no sense to me that if the speed of light is always c...then in different mediums why this speed changes...?? I may have got it in a wrong way...But can anyone help me out in detail...(thanks)

Please start by reading the FAQ thread in the General Physics forum.

Zz.
 


The speed of light is constant in vacuum and it changes in different mediums.
when light enters a denser medium (like from air to glass) the speed and wavelength of the
light wave decrease while the frequency stays the same.
How much light slows down depends on the new medium's refractive index, n.
 


speed of light (c = 3 x 10^8) is an constant while on vacuum
but c vary in other medium depend on its density. => n = c/v while n = refractive index.
higher refractive index means less density.
CMIIW
 


quantizedzeus said:
It makes no sense to me that if the speed of light is always c...then in different mediums why this speed changes...?? I may have got it in a wrong way...But can anyone help me out in detail...(thanks)

Seems perfectly natural to me. But don't just say the speed changes. It only gets slower in a medium.

But the fact is that light is constantly absorbed and re-emitted in a medium. The light that goes out isn't the light that came in.

When a light-particle bangs into the electron cloud in an atom in a medium, it dies and is disappeared, and an impostor steals its clothes and runs out the same direction a bit later. Everyone is fooled. Even the cops.
 


danR said:
Seems perfectly natural to me. But don't just say the speed changes. It only gets slower in a medium.

But the fact is that light is constantly absorbed and re-emitted in a medium. The light that goes out isn't the light that came in.

When a light-particle bangs into the electron cloud in an atom in a medium, it dies and is disappeared, and an impostor steals its clothes and runs out the same direction a bit later. Everyone is fooled. Even the cops.

Speed of light is slower in all mediums except VACUUM.
v=frequency x wavelength

v changes but wavelength doesn't.

as v changes this causes refraction when light enters a different medium.
 


Keyur said:
Speed of light is slower in all mediums except VACUUM.
v=frequency x wavelength

v changes but wavelength doesn't.

as v changes this causes refraction when light enters a different medium.

I wouldn't include a vacuum as a medium, though. And strictly speaking, does c remain as a constant even with a medium, between re-emissions and re-absorptions?
 
  • #10


After reading the FAQ on transmission through a medium, I have to abandon the simple adsorbtion, re-emission model, although the wording at a key point in that article is a bit confusing.
 
  • #11


danR said:
Seems perfectly natural to me. But don't just say the speed changes. It only gets slower in a medium.

But the fact is that light is constantly absorbed and re-emitted in a medium. The light that goes out isn't the light that came in.

When a light-particle bangs into the electron cloud in an atom in a medium, it dies and is disappeared, and an impostor steals its clothes and runs out the same direction a bit later. Everyone is fooled. Even the cops.

so the light particle that come in will stay there ?? or what ?
 
  • #12


If the light bulb is in the midle of the room and you turn it on the light reaches south wall same time as north wall. Does that mean you multiply the speed of light times 2?
 
  • #13


No, it doesn't. Speed is measured from one object to another. Not from one object to two others at the same time. That's not speed.
 
  • #14


piroman said:
If the light bulb is in the midle of the room and you turn it on the light reaches south wall same time as north wall. Does that mean you multiply the speed of light times 2?

You need to read up on what light is. Hit up wikipedia and the FAQ here on PF.
 

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