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.