On a clear day, the sky appears to be more blue toward the zenith (overhead) than it does toward the horizon. This occurs because
A) the atmosphere is denser higher up than it is at the earth's surface.
B) the atmosphere is more reddish over the ocean.
C) the temperature of the upper atmosphere is higher than it is at the earth's surface.
D) the sunlight travels over a longer path at the horizon, resulting in more absorption.

Question

Quizplus · Accepted Answer

The sunlight travels a longer path through the atmosphere when you look towards the horizon compared to when you look directly overhead (zenith). This longer path causes more scattering of shorter wavelengths (blue light) by the atmosphere, making the sky appear less blue and more reddish or pale near the horizon.

On a Clear Day, the Sky Appears to Be More