'It's the material, Not the colour!' - How do we see colours?

 "Life is like a rainbow. You need both the Sun and the Rain to make it's colors appear!"

  As this quote depicts that a rainbow is the result of reflection of sun's light by the water droplets, the color of an object is seen by the wavelength of light that falls on it.

• Visible light is an electromagnetic radiation between the wavelength range of 400nm to 700nm.

• The human brain can distinguish up to 100 millions of colors depending upon the combination of wavelengths of visible light reaching our eyes.

• Longer wavelength region (700nm) have Red color and as the wavelength reduces it changes to Orange, Yellow, Green, Blue-green, Blue, Indigo and Violet (400nm).

• The major source of visible light for the Earth is Sun.

• We receive white light (combination of VIBGYOR) from Sun.

What actually happens?

When light falls on an object, not all the light gets reflected. Some frequency range of light is absorbed by the object. Only the reflected frequency of light are visible to our eyes and that is the color of the object.

For example,

Let us consider a red apple. When sunlight falls on it, all the frequencies gets absorbed by the apple except the frequency corresponding to red color which is reflected. So apple appears ‘red’ to us.

Perfect black object: The object which absorbs all the frequencies of the visible spectrum and does not reflect is called a perfect black body and it will be invisible.

Perfect white object: The object which reflects all the frequencies of the visible spectrum and does not absorb any. But in reality there is no perfect white or black objects. 

A fascinating question,

What will happen when a violet color object is placed in a red room? 

The answer is, Basically the violet colored object reflects only the violet color. But since the room is illuminated with red light, the violet colored object absorbs the red frequency and reflects back nothing. So the object appears black in color.