How rainbows are created

WSAV NOW Weather

SAVANNAH, GA (WSAV) — Everyone loves to see a rainbow after a storm. Did you know rainbows are just an optical illusion? They don’t actually exist in a specific spot in the sky. In this episode of Exploring the Atmosphere with Alysa, you’ll learn the perfect placement to see a rainbow, how they are created, and 2 fun rainbow inspired experiments that you won’t want to SKITTLE out on!

TO SEE A RAINBOW

To see a rainbow, you need 3 things: rain, sunshine, and your own eyes. For a rainbow to be created, sunshine has to shine into a raindrop. Light then has to bounce off that drop and into your eye. If you want to see the rainbow, you have to be standing where your eyes can catch the colored light.

This means you have to be standing in between the sun and the raindrops, with the sun behind you. After a summer storm, look for a rainbow opposite in the sky of the sun. The lower the sun is in the sky, the higher the rainbow’s arc will be.

HOW RAINBOWS ARE CREATED

REFRACTION

On a bright sunny day, sunlight might look like it is one bright color. Sunlight, however, is actually made up of different colors of light mixed together. We can remember the colors of the rainbow by using this name: ROY G BIV (Red, Orange, Yellow, Green, Blue, Indigo, & Violet).

We see those different colors of light in waves. Those waves come in different sizes called wavelengths, with each color having a different wavelength. For example, violet light has a shorter wavelength than red light. 

This is because when light enters water at an angle, it changes directions. This is called REFRACTION or bending of light. The sunlight is then separated into different wavelengths. Some wavelengths bend more than others when sunlight hits a water droplet. The amount of light bends depending on the color’s wavelengths.

The shorter the wavelength of the color, the more it changes direction. With violet having a shorter wavelength than red, it will change direction more than red light. 

REFRACTION causes all the colors in a rainbow end up separating into their separate wavelengths when sunlight hits a raindrop.  This is why red is on top of the rainbow and violet is on the bottom.

REFLECTION

Reflection works in 2 parts in a rainbow. When you see a rainbow, you’re actually seeing light that has hit thousands of tiny raindrop and is then bounced back into your eye. For a rainbow to form, light has to be reflected at certain angles inside a raindrop. Due to the angle of refraction of water, sunlight is reflected most strongly at 42 degrees.

The second part is how the rainbow’s arc is created. The sun’s light starts off by hitting thousands of raindrops in the sky at once. Once sunlight is reflected back into your eye at those certain angles, the rays will then start to form an arc in the sky. The arc is created by both reflection and refraction working together.

The tiny raindrops are now acting like prisms as the sun shines into them. As refraction bends the colors of light, each raindrop prism disperses the sunlight due to the reflection angle and reflects it back to you in a arc like shape.

The lower the sun is in the sky, the higher the rainbow’s arc will be. We don’t see a full circle because the Earth gets in the way. If you were up in an airplane looking at the ground, you would see a complete rainbow circle!

REFLECTION gives you the shape of the rainbow, while REFRACTION gives you the colors!

EXPERIMENTS

WATER IN A GLASS

This experiment is super simple. All you need is a glass cup, water, and sunshine.

HOW TO:

  • Fill the glass with water. 
  • Position the glass so the sunlight shines directly into the glass. 
  • Look for a reflection on the wall or table. It would be easier to see if the room is dark. 
  • Adjust the angle until you see the rainbow.   

You can also easily do this with a garden hose! Just put your back to the sun, have the setting on mist, and enjoy!

SKITTLE EXPERIMENT

This is such a fun experiment that incorporates rainbow science and sugar science, plus you get to eat skittles!

Supplies:
– Water (will need to be heated)
– Mug
– 5 Separate Cups
– Tablespoon
– Clear Glass
– Box of Skittles

EXPERIMENT

  1. Start off by separating the skittles into colors…you’ll need 2 red, 4 orange, 6 yellow, 8 green, & 10 purple.
  2. Put those skittles into 5 cups by color.
  3. Next, you’ll need hot water. Make sure the water is NOT boiling.
  4. Pour 2 tablespoons of hot water into each cup on top of the skittles.
  5. Stir each cup carefully to mix the water and the skittles.
  6. Let each cup cool until the water is room temperature. Stir them every 10 minutes until the skittles are completely dissolved in the water.
    *TIP: You might need to add 1/2 tablespoon of water for the green and purple skittles since there are so many of them*
  7. Once the skittles are completely dissolved, take the clear glass and add the purple skittle water.
  8. Hold the glass at an angle and carefully (& slowly) pour the green skittle water down the side of glass.
  9. Repeat step 8 for the yellow, then orange, and lastly red skittle waters. Be very careful as you pour the water in so you don’t mix the colors.
  10. Congrats you’ve made a rainbow!

I wouldn’t say taste the rainbow water, but enjoy the left over skittles!

HOW THIS WORKS

Skittles are made out of mainly sugar. When you add hot water to the skittles, the sugar and the coloring of the outside of the shell dissolves. The coloring of the shell is what turns the water different colors.

The cup with 2 red skittles doesn’t have as much sugar in the cup compared to the cup with 10 purple skittles but they have the same amount of water. The amount of matter packed into a certain amount of space is called the density of material. The red water is less dense than the purple water, so the red water will float on top of the purple water. 

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