Why do objects appear coloured?

          Do you know why an apple or tomato appears red, the grass green, and the milk white when they are all illuminated by the same sunlight? In fact, the colour of an object depends upon the colour it reflects.

          The sunlight which appears white comprises of seven colours: violet, indigo, blue, green, yellow, orange and red. In sunlight, an apple or tomato appears red because it reflects only the red colour and absorbs the rest.

Grass appears green because it reflects only the green colour and absorbs all other colours present in the sunlight. A white shirt or milk appears white because it reflects all the colours of the sunlight. And a blackboard appears black because it absorbs all the colours of white light and reflects none. To prove this, focus red light on a white shirt and you will see that it becomes red. White objects take the colour of light falling on it. Similarly if we see an apple in red or white light it will appear red but in green or blue light it would appear black. It cannot reflect any other colour but red and, therefore, looks black in any other colour except red or white. This is how the various objects get their colour.