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Find out why the sky is blue in this science experiment

Suitable For

Grade 2



Time Required

 <1 Hour



What’s it about?

When you look up to the sky on a clear and sunny day, you see that the sky appears bright blue. You become fascinated by its beauty and ask yourself why the sky is blue. As the day passes and sunset arrives, you notice that the bright blue sky has turned into a combination of reds, oranges, and pinks. In the following science experiment learn what causes the various colours of the sky:

Topics covered

Atmosphere, Rayleigh scattering, Colour spectrum

What will I need?

  • MILK

Procedure (Method)

Unfortunately, this section is only available in the e-book version of the project.

How does it work?

Unfortunately, this section is only available in the e-book version of the project.

In this science experiment, milk is added to the water so that the light from the flashlight is more easily seen because the particles in the milk reflect the light. When the milk / water solution is viewed from the top, it appears to be a light blue colour because the particles separated out the blue waves of light.

Similarly, the earth’s atmosphere contains tiny drops of water and small particles of dust which causes the light from the sun to bend, resulting in the familiar blue skies! An effect called ‘Rayleigh scattering’ is when the molecules contained in the atmosphere scatter the different wavelengths of light coming from the sun. Abundant molecules in the atmosphere such as nitrogen and oxygen reflect light waves with shorter wavelengths, like violet and blue, much better than the longer wavelengths like red or orange. Wherever you look in the sky during the day, you can see scattered blue light overhead.

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