Science Behind Rainbows

Rainbows form when sunlight passes through raindrops in the sky. This process involves three key steps: 

Refraction: When sunlight enters a raindrop, it slows down and bends. This bending of light is called refraction. 

  • Different colors of light bend by different amounts because they have different wavelengths.

Reflection: Inside the raindrop, the light hits the back of the drop and bounces back. This is called reflection. 

  • The light is now heading out of the drop but is still inside.

Dispersion: As the light exits the raindrop, it bends again. This second refraction causes the light to spread out into its different colors, creating a spectrum. 

  • This spreading of light into colors is called dispersion.


Why Are Some Rainbows Brighter?

  • First, when the sunlight is very strong, it can make a rainbow look brighter. 
  • Second, if the raindrops are bigger and there are more of them, the rainbow will be more colorful. 
  • Finally, rainbows that are closer to the horizon (lower in the sky) often look brighter because the light travels through more air.

How Do Rainbows Disappear?

The rainbow will fade away if the rain stops or clouds block the sunlight. 

Nothing can bend the light without sunlight and raindrops and create the colorful arc we see in the sky.

Fun Facts

Here are some interesting facts about rainbows:

  • You can sometimes see a full circle rainbow from an airplane or a high viewpoint. 
  • Rainbows can also be formed by the moon’s light. These are called moonbows or lunar rainbows and are much fainter than those created by sunlight.
  • Sometimes, you can see a rainbow without rain, like near waterfalls or fountains, where water droplets are in the air.


Let’s quickly recap what we learned about rainbows:

  • What is the bending of light through a raindrop called? Refraction
  • What is the process through which the light hits the back of the drop and bounces back? Reflection
  • What is the spreading of light into different colors called? Dispersion
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