The passage mainly explains

why the sky looks blue and sunsets look red (The whole passage uses scattering to explain both the blue sky and the red sunset.)

According to the passage, which colors scatter most strongly?

Blue and violet (The text says the short waves of blue and violet 'scatter far more strongly' than red and orange.)

Based on the passage, if the air held no gas molecules, the daytime sky would most likely

look dark, since nothing would scatter the sunlight (The blue comes from molecules scattering light; with no scatterer, no blue would fill the sky, leaving it dark.)

In this passage, 'scattering' most nearly means

light bouncing off in new directions (The text defines it in place: gas molecules 'send it bouncing off in new directions, a process called scattering'.)

Why the Sky Is Blue: Level 3 Reading Comprehension Questions

Sunlight looks white, but it is really a blend of many colors mixed together. When that light passes through the air, it does not travel untouched. Tiny molecules of gas bump the light and send it bouncing off in new directions, a process called scattering.

Not every color scatters the same amount. The blue and violet parts of sunlight travel in short, tight waves, and these short waves scatter far more strongly than the long, slow waves of red and orange. So as sunlight crosses the sky, blue light is thrown in every direction, filling the whole dome above you. When you look up, that scattered blue is the light reaching your eyes, and the sky appears blue.

The same rule explains the red of a sunset. Near the horizon, light must pass through much more air before it reaches you. Along that longer path, most of the blue has already been scattered away, leaving mainly the reds and oranges to come through. One simple fact about wave length, then, paints both the blue of noon and the red of evening.

Comprehension questions