Light and colour
Why do we see things in colour, not black and white?
Light such as sunlight contains the full electromagnetic spectrum, but our eyes are only sensitive to a wavelength of approximately 390 to 700 nanometres (nm), known as visible light. As sunlight shines on an object, such as a green apple, the object absorbs some of the incident light – the direct light that hits the surface. However, it reflects a specific wavelength of light, in this case corresponding to the colour green, which is received by sensors in the eyes known as rods and cones. These tell the brain that the colour of the object is green.
White paper appears white because it reflects all visible light. We see black when all visible light is absorbed by an object. Certain pigments within an object will absorb light and define which wavelengths they will emit. The primary colours of red, blue and green combine to create the many different colours that we see.