Let’s make a rainbow in your living room with your kids.

1. Fill a glass or acrylic case of water and setup on the table. 

2. Turn on a flashlight with a slit. 

   Although the slit is not necessary to make your rainbow, but it’s desirable. 

3. Shine the light across the water. 

   Then, the tilt angle of approximately 20 degrees would be effective. 

Can you observe the red to blue light (visible spectrum)? 

Let’s learn the blue light has relatively large refractive index than for red. 
 
We can understand why the sky of the sunset is red, or why the sky is blue. 
Here is a tip. Let’s consider the length of atmospheric layers. 
 
Hope you and your kids enjoy the exam.