# Why we see different colours

1. May 22, 2004

### repugno

Hello all,

I’m interested in finding out why we see different colours. I know that different colours arise from different wavelengths of electromagnetic waves. But why are objects different colours if the light reflecting comes from the same source? Is it because the objects absorb some of the light thus altering the wavelength of the wave and so we see a different colour? What is the reason? Any help would be much appreciated. Thanks

2. May 22, 2004

### mathman

White light contains all colors. When we see an onject of a given color, it means that color is reflected and others are absorbed. You also have to realize when we see something of a given color, it is not usually a single frequency, but a mixture which looks to us the color we see.

3. May 23, 2004

### Gokul43201

Staff Emeritus
The absorption of light by a material depends on (among other things) a property known as its dielectric constant. This number veries with the frequency of the incident light. Hence, any given material absorbs more in certain frequencies and less in others. What is not absorbed is either transmitted through the material (this happens a lot in glass) or reflected. The frequency distribution of this unabsorbed light is what determines the color of the material.

4. Jun 4, 2004

### JohnDubYa

Keep in mind that the color you see is actually a biological phenomenon. Just because you see green does not necessarily mean that your eyes are sensing light of a particular wavelength. Different combinations of wavelengths can produce this same sensation.

5. Jun 4, 2004

### Clausius2

I have an stupid question:

Has the black color a a wavelenght defined?.

6. Jun 4, 2004