Colour of Sunlight: White or Coloured?

The gorgeous red hues of sunrise at dawn, the golden white shimmering towards noon, or the brilliant tangerine winter sunset over a snowy field, the sun never ceases to awe us with its display of colours! But have you ever given thought to the range of colours that you witness every day? When asked about the colour of sunlight, a reflexive response would be, ‘yellow’ or ‘white’! You might also answer ‘red’ or ‘orange’ if ‘dawn and dusk’ pop up in your mind’s eye. Nevertheless, what really is the colour of sunlight?

Demonstrating the Colour of Sunlight through an Experiment

Let us demonstrate the colour of sunlight through a small activity.

Requirements: A Prism and a White Sheet of Paper

• Take a glass prism in a dark room
• Place it in a position such that the direct sunlight falls on it through a hole in the window shutter of the room.
• Fix the white paper on the opposite wall where the sunlight is reflected through the prism.

We observe on the paper that the sunlight is split into a spectrum of colours. Pretty much like the rainbow, every colour in VIBGYOR, that is, Violet, Indigo, Blue, Green, Yellow, Orange and Red, can be seen. The conclusion drawn here is that sunlight is nothing but a mixture of seven colours. And these seven colours combine to form the white light.

Why Don’t We See Sunlight as Seven Colours?

When the sun’s rays enter the earth, they get distorted by the earth’s atmosphere, air molecules, dust, smoke and pollution. We know that different colours of the spectrum have different wavelengths. The short-wavelength blue and violet are scattered more than colours at the lower end of the spectrum, which are less easily scattered.

• Noon

  : If the sun is high overhead in the sky, the rays suffer the least amount of interference because the distance covered by them is the least at that point in time. Consequently, the blue light is scattered, and the sky appears blue, whereas the colour of sunlight appears yellow.

• Morning and Evening

  : During the sunrise and sunset, the sun is near the horizon, due to which the light rays have to travel a longer distance through the atmosphere. As a result, there is more interference which causes more scattering. Consequently, most of the colours, including blue as well as yellow, are scattered, leaving the red light. Hence, the colour of sunlight appears in the tinges of orange and red during dawn and dusk.

Learn about Refraction of Light with BYJU’S.