Today we are going to teach you how to create your own rainbows – rain or shine, day or night!
To start this experiment all you need is:
- A clear, smooth sided, drinking glass or glass vase, filled almost to the top with water
- A source of light (this can be the sun, a bright flashlight, or other light source)
- A dark room
Begin by filling a drinking glass or vase full of water.
Next, you will need to cut a slat in your sheet of paper (you will want to cut a vertical, thin rectangular shape).
Secure your slatted piece of paper to the outside of the glass so that it is centered more closely to the top of the glass.
Turn on your flashlight, and shine it down at an angle so that the light hits the top of the water in the glass and — find your rainbow! It depends upon where your light angle hits the water and reflects unto the surface below as to how far away your rainbow will appear. Try moving your flashlight closer and farther away as well as adjusting the angle to the water to see the best rainbow.
What’s the science?
You probably noticed that this doesn’t look like your average outdoor rainbow. The flashlight’s ray contains different colors that create light (such as red, orange, yellow, green, blue, and purple). When you shine the light through the water, it bends, or refracts, and separates into the different colors. This is because the different colors (or wavelengths) of light behave slightly differently as they travel through our variables of water and glass. Notice the order of the colors is exactly the same as they are in a rainbow you see after a rain storm? This is because each color has a different wavelength with red having the longest wavelength, and violet the shortest. This is why red is at the top of the arch and violet is at the bottom.
Remember, it is important to note that an experiment uses a variable (something that changes) to answer a question. To turn this demonstration into an experiment, you have to change something! Check out these questions to get you started:
- How does the placement of the paper affect the outcome?
- Do different light angles change the size of the rainbow?
- Does the size or shape of the glass affect the size or shape of the rainbow?
Give it a try and let us know how your experiment turned out on our Facebook, Instagram, or Twitter pages using the hashtag #gscscience!