What is Colour ? How human eye see different colours ?

What is Colour ? How human eye see different colours ?

Ans - Colour is Light. Colours are different wavelength of Reflected Visible Light.

The most important source of light on earth is SUN. Sun releases excess heat energy in forms of light. This light travels in different wavelength with different frequencies.Everything we see is different wavelength of reflected visible light.

Light released by Sun

What is Visbile light ?

The light that is visible to human eye is called visible light.A typical human eye will respond to light wavelength range 380nm to 750nm , in terms of frequency band it would range 400THz to 790THz , but there are more lights which are invisible to human eye like gamma wave , x ray , ultra voilet wave , infrared wave , radio wave etc.

Actual visible light wavelength

We call ordinary sunlight as white light but it actually includes all the colours that can be seen by human eye. This can be tested by passing white light through a prism as shown in below image.

White light on prism

When we look an object we actually see the colour that is reflecting from the object.

For example,
If we see any red object it means it absorbs all the light wavelengths except wavelength with red colour.

Things that look white means all the lights are reflected by the object and if things look black means all the lights are obsorbed by that object so it looks black in colour.

In visible light red colour has the longest wavelength 750nm and voilet colour has the shortest wavelength 380nm.

Colours wavelength

Rainbow colours are best example for all visible light colours

Rainbow has all visible light colours