changes in light properties betw different index of refraction

[ihatebluescrubs]

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So, after doing this question in Berkeley Review Physics Chap 10, #11 I got confused on a concept regarding what changes in the properties of light when moving from a medium to another medium.

Basically the question was asking about the properties of light when passing through 3 different mediums stacked together top has low n(index of refraction), medium layer has high n, and bottom layer has low n. The question asked to determine how frequency changes and the answer was that it stays constant.


My question is this: we know that n=c/v. When light moves from one medium to another (ex: air to glass: low n to high n), velocity of the light decreases since n increases. Now we know that v=wavelength*frequency. Why doesn't frequency change? If frequency doesn't change, then I assume wavelength changes? Is that right?

Thanks!

 

[AFLATPEG]

So, after doing this question in Berkeley Review Physics Chap 10, #11 I got confused on a concept regarding what changes in the properties of light when moving from a medium to another medium.

Basically the question was asking about the properties of light when passing through 3 different mediums stacked together top has low n(index of refraction), medium layer has high n, and bottom layer has low n. The question asked to determine how frequency changes and the answer was that it stays constant.


My question is this: we know that n=c/v. When light moves from one medium to another (ex: air to glass: low n to high n), velocity of the light decreases since n increases. Now we know that v=wavelength*frequency. Why doesn't frequency change? If frequency doesn't change, then I assume wavelength changes? Is that right?

Thanks!

yes!

wavelength changes, NOT frequency.

remember, frequency doesn't change for ANYTHING (sound or light), EXCEPT for Doppler.

 

[ihatebluescrubs]

Thanks!

Also did even more googling and found a thread similar to my question: http://forums.studentdoctor.net/showthread.php?t=845091


I have a followup question: When wavelength changes, does this have to do with why white light splits into different color lights? When the wavelength changes, does that mean that in that particular medium, we'll see the light ray in a different color?

 

[milski]

Thanks!

Also did even more googling and found a thread similar to my question: http://forums.studentdoctor.net/showthread.php?t=845091


I have a followup question: When wavelength changes, does this have to do with why white light splits into different color lights? When the wavelength changes, does that mean that in that particular medium, we'll see the light ray in a different color?

No, at least not directly. You see different colors because before the change in media all colors of light are following exactly the same path and your eyes perceive this as white. Once the beams with different frequencies start following different paths you can distinguish between these paths.

 

[adrakdavra]

you need to consider three things,
1)photons in light for example Red photons carry about 1.8 electron volts (eV) of energy, while each blue photon transmits about 3.1 eV. 2)Light waves are the result of vibrations of electric and magnetic fields. 3) sensitivity of your eye cones and rods.
Light and Color unit that each color is characteristic of a distinct wave frequency; and different frequencies of light waves will bend varying amounts upon passage through a prism. light wave traveling through a transparent material interacts with the atoms of that material. it also depends on optical density ( every medium has its own.
The optical density of a material is the result of the tendency of the atoms of a material to maintain the absorbed energy of the light wave in the form of vibrating electrons before re-emitting it as a new electromagnetic disturbance.
The absorption and re-emission process causes the higher frequency (lower wavelength) violet light to travel slower through crown glass than the lower frequency (higher wavelength) red light.

 

[Deadlifts]

While what everyone said is valuable information for other MCAT physics questions, the question is much more straight forward.

Just to elaborate a little bit on AFLATPEG's initial response, if they ever ask about frequency check the question for any changes to the wave SOURCE. A change in frequency requires a alteration of the source (hertz, don't it?). OP, you used the correct equation relationships; just have to realize that frequency is source dependent while wavelength is affected by medium (if the prism refraction isn't visualizing well, think of the differences in the speed of sound in air versus water and what happens to the wavelength).

Then there's Doppler where your perceived frequency changes based on motion towards/away but those questions are worded fairly obviously and not relevant to this discussion. 🙂

 

[AFLATPEG]

While what everyone said is valuable information for other MCAT physics questions, the question is much more straight forward.

Just to elaborate a little bit on AFLATPEG's initial response, if they ever ask about frequency check the question for any changes to the wave SOURCE. A change in frequency requires a alteration of the source (hertz, don't it?). OP, you used the correct equation relationships; just have to realize that frequency is source dependent while wavelength is affected by medium (if the prism refraction isn't visualizing well, think of the differences in the speed of sound in air versus water and what happens to the wavelength).

Then there's Doppler where your perceived frequency changes based on motion towards/away but those questions are worded fairly obviously and not relevant to this discussion. 🙂

👍 🙂