One morning, Trish and her father went for a stroll in the green 
park. She looked up at the sky and marveled at its beauty. The sun was 
shining brightly. The thin clouds moved slowly in the air. The sky was clear
and blue. Trish wondered why. She then turned to her father and asked "Dad,
why does the sky appear in blue color? Why is it not yellow or white like 
the sun?

Her father answered, "Well, the light coming from the sun only appears to be
white. It is actually a combination of all the colors of the rainbow."

"Oh. but why it appears in blue color and not the other colors of the
rainbow? Trish asked.

"You see, light travels as a wave. Each color of the light that comes from
the sun has its own wavelength. Wavelength is the distance between the two
peaks of the wave. Red light has a long wavelength, while violet and blue
lights have short wavelengths, "Trish dad explained.


"What happens when these colors reach our atmosphere?" Trish asked. Her dad
replied, "There are many particles in the atmosphere. There are air, dust, 
and tiny water molecules. When sunlight reaches Earth's atmosphere, the 
particles scatter the light in different directions."

"So you mean all the colors of the rainbow are actually scattered in the 
atmosphere?"

"That's right! But blue light travels as shorter and smaller waves than the
other colors. Because of this, it is scattered in more directions all over
the sky. That is why sky appears to be blue most of the time."

Trish exclaimed, "Now I understand! Good thing the sky appears blue! I 
cannot imagine a green sky!"