The Sky is Blue:

* Rayleigh Scattering: Sunlight is made up of all the colors of the rainbow. When sunlight enters the Earth's atmosphere, it collides with tiny gas molecules (nitrogen and oxygen).

* Shorter Wavelengths Scatter More: Blue light has a shorter wavelength than other colors. These shorter wavelengths scatter more strongly by the gas molecules in the atmosphere.

* Scattered Light Reaches Our Eyes: This scattered blue light is what we see as the blue sky.

Grass is Green:

* Chlorophyll: Plants contain a pigment called chlorophyll, which absorbs most wavelengths of light except for green.

* Reflection: Green light is reflected back, which is why we see grass as green.

* Other Pigments: Grass also contains other pigments that contribute to its color, but chlorophyll is the dominant one.

Why the Sunset is Red:

* Longer Path: As the sun sets, the sunlight has to travel through a longer path in the atmosphere to reach our eyes.

* Scattering: Blue light is scattered away more, leaving the longer wavelengths like red and orange to reach us.

Let me know if you'd like to explore these concepts in more detail!