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Why Is the Sky Blue? — Reading Comprehension

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This NGSS-aligned reading passage explains why the sky appears blue by introducing middle school readers to the science of Rayleigh scattering. Students will explore how sunlight contains all colors of light and how shorter wavelengths like blue are scattered more in Earth’s atmosphere. The passage also explains the role of air molecules, why we don’t see violet skies, and why sunsets appear red or orange. It supports NGSS standard MS-PS4-2 and builds understanding of light behavior and the visible spectrum through engaging, age-appropriate content.

CONTENT PREVIEW

When you look up on a clear day, the sky usually looks bright blue. But have you ever wondered why? The answer has to do with light and the way it travels through the atmosphere.

Sunlight may appear white, but it’s actually made up of all the colors of the rainbow—red, orange, yellow, green, blue, indigo, and violet. Each of these colors travels in waves, and some waves are shorter than others. Blue and violet light have the shortest wavelengths, while red and orange have the longest.

As sunlight enters Earth’s atmosphere, it hits tiny gas molecules, like oxygen and nitrogen. These molecules scatter the light in different directions. This process is called Rayleigh scattering. Because blue light has a shorter wavelength, it gets scattered more than the other colors.

Even though violet light is scattered more than blue, our eyes are more sensitive to blue—and some violet light gets absorbed by the upper atmosphere.

As a result, when we look up during the day, we see more scattered blue light coming from all parts of the sky.

At sunrise and sunset, the sky looks red or orange because the sunlight has to travel through more atmosphere. Most of the blue and violet light gets scattered away, so only the longer wavelengths like red and orange reach our eyes.

The blue sky is a beautiful reminder of how light and air work together to create the colors we see every day.

Fun Fact: Mars has a thin atmosphere and lots of dust, so its sky appears reddish during the day and bluish at sunset—the opposite of Earth!

What is sunlight made of?

Only blue and red lightJust white lightAll the colors of the rainbowHeat and water vapor

Which type of light waves are scattered the most?

Red and orangeGreen and yellowBlue and violetInfrared and UV

What causes sunlight to scatter in the atmosphere?

Clouds blocking the sunAir pressure pushing lightGas molecules like oxygen and nitrogenWater droplets freezing

What is the name of the scattering process mentioned in the passage?

Light reflectionHeat radiationRayleigh scatteringAir splitting

Why don’t we see a violet sky even though violet light scatters more than blue?

It disappears in spaceOur eyes don’t see violet wellThe sun only shines blueOxygen blocks violet light

Why does the sky look red or orange at sunset?

The sun burns brighter at nightBlue light reflects off the moonSunlight passes through more atmosphereClouds change color

What is the main idea of the passage?

The sky changes color during the seasonsThe blue sky comes from how light scatters in airThe sky is blue because of the oceanThe sky is always one color

What might happen if Earth had no atmosphere?

The sky would still be blueThe sky would look purpleThere would be no sky color—just blacknessThe sky would turn green