Question

Why sky and sea look blue tells us in brief

Answer 1

Why is the sky blue?

In my experience, this is one of the most frequently asked questions. The short answer is: Rayleigh scattering. Okay, so what the heck is Rayleigh scattering?

As you may know, our air is made up mostly of nitrogen and oxygen molecules. There’s a small amount of water vapor, carbon dioxide, argon, and other gases as well, but it’s 99% N2 and O2. You might also know that sunlight is made of many different colors of light — in fact, all the colors of the rainbow are in sunlight.

When sunlight passes through air, it gets “scattered” a bit. What’s really happening is that the light is interacting with air molecules, and the molecules cause the light to spread out. Red, orange, yellow, and green light don’t scatter very much, but blue and violet light do. In fact, blue light scatters so much that it seems to be coming at you from every direction when the Sun is in the sky. That’s why the sky looks blue on a cloudless sunny day.

Now you might ask: if violet light gets scattered too, why doesn’t the sky look more blue-violet? Well, the intensity of the violet light isn’t as strong as the intensity of the blue light; plus, our eyes aren’t as sensitive to violet light as they are to blue. So the blue strongly overwhelms the violet in our vision.

Answer 2

Sky and water look blue due to the reflection of water and sky.