# If a light goes from space to a glass

If a light goes from space to a glass his wavelength becomes smaller.So if we put a red color to a glass it can become orange?

Drakkith
Staff Emeritus
No. The frequency remains the same, as does the energy of the wave. It does not change color.

Bandersnatch
Light does not change wavelength as it moves from one medium to another. It changes path. If you light a torch, or a laser pointer from a side of an aquarium, the light beam retains the same colour, but follow a line at an angle to the original path. It's called refraction.
http://en.wikipedia.org/wiki/Refraction)

It does change wavelength, but not frequency or color.

Bandersnatch
It does change wavelength, but not frequency or color.
Wavelength, frequency, and colour are all pretty much the same thing, so one cannot change without the others.
Frequency is the inverse of wavelength(f=1/λ), and colur is the perception of specific wavelengths.

Dale
Mentor
2020 Award
Light does not change wavelength as it moves from one medium to another.
This is not correct, it does change wavelength.

Drakkith
Staff Emeritus
Wavelength, frequency, and colour are all pretty much the same thing, so one cannot change without the others.
Frequency is the inverse of wavelength(f=1/λ), and colur is the perception of specific wavelengths.

No, wavelength can change while the frequency remains the same: http://en.wikipedia.org/wiki/Frequency#Frequency_of_waves

When waves from a monochrome source travel from one medium to another, their frequency remains the same—only their wavelength and speed change.

Bandersnatch
I stand corrected on both accounts.

I knew that only speed and wavelength change and that frequency remains the same.but I knew that color is about wavelength so something with 700nm is red.then if wavelength change ,color?

Dale
Mentor
2020 Award
The only place you see color is inside your retina and it is only the wavelength there that matters. The wavelength there is determined by the frequency of the light and the index of refraction of the vitreous humor.

When waves from a monochrome source travel from one medium to another, their frequency remains the same—only their wavelength and speed change.

So, if colour is the function of the wavelength, why don't color change when wavelength changes?

Drakkith
Staff Emeritus
So, if colour is the function of the wavelength, why don't color change when wavelength changes?

Because that isn't strictly correct. It would be more accurate to say that color changes when the frequency changes, as the frequency doesn't change between emission and absorption, no matter what material the light enters.

But, there are cases where the frequency does change, and so does the color. For example, take the doppler shift of light when traveling towards or away from a light source. There is both a frequency AND a wavelength change, which will change its color as well.

meBigGuy
Gold Member
The frequency of light does not change in different mediums. The wavelength changes because the speed of light though the media changes.

But, to take the point 1 furthur, you cannot see the light in glass. You can only see light that enters your eye, in which case it is no longer in glass.

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