Answer:
The Short Answer: Sunlight reaches Earth's atmosphere and is scattered in all directions by all the gases and particles in the air. Blue light is scattered more than the other colors because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
Explanation:
When light moves from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle above which there is no refracted light, and all the light is reflected. The value of this angle is given by

where n2 and n1 are the refractive indices of the second and first medium, respectively.
In the first part of the problem, light moves from glass to air (

) and the critical angle is

. This means that we can find the refractive index of glass by re-arranging the previous formula:

Now the glass is put into water, whose refractive index is

. If light moves from glass to water, the new critical angle will be
The sum of an object's potential and kinetic energies is called the object's mechanical energy. As an object falls its potential energy decreases, while its kinetic energy increases. The decrease in potential energy is exactly equal to the increase in kinetic energy.
How dense the medium is in the compression part of the wave and how rare the medium is in the rarefaction part of the wave is a measure of the longitudinal wave's amplitude.