The sun's power??

Question

here's my questions bout the sun!!


1. Is the air heated directly by sunlight? Explain your answer.

2. Explain the Law of Inverse Squares.

3. When and why does earthshine occur?

Answer 1

cfpops answered 1 and 2 adequately, but I think I can elaborate a bit on 3:
Earthshine is not quite the same thing as albedo. Albedo is the measurement which deals with how much light is reflected by a planet (or in simpler terms, how "shiny" it is). And the earth does have a very high albedo due to so much water covered surface area.
Earthshine, however is not a measurment of reflectivity, but is the actuall light that has been reflected. It can best be seen indirectly from the earth during early waxing crescent or late waning crescent phases of the moon, just a few days to either side of the new moon.
You can see the lighted portion of the moon quite easily, but if you look closely, you can also see the unlighted side of the moon appearing just a shade or two lighter than the night sky.
What you are seeing is light that has been reflected off the earth's oceans, the "earthshine" and is lighting up the dark side of the moon.
Now, to be thorough, just as cfpops said, the atmosphere is directly heated by sunlight. The heat from the sun in the form of infrared light excites the air molecules quite a bit. But the air is also indirectly heated by sunlight in that the sun's rays warm the land and the seas and the heat is then transferred to the atmosphere. To be honest, I seem to recall the a fair amount of the heat in the atmosphere comes from indirect heat transfer. That is to say, the sun warms the land and seas and they in turn warm the air.
As for the Inverse Square Law, it is simply a matter for all waves, heat, light, radio, etc. that waves get weaker with the square of the distance from the source. For example, if you stood 10 meters from a light bulb and measured the power of the light bulb at 100 watts, then moved to 20 meters distance, the power of the light bulbe would be 4 times weaker (twice the distance, squared) and you would only measure 25 watts. Add another 10 meters, and the power would be 1/9 of the original measurment (three times the distance, squared).
Hope that makes things clear.

Answer 2

1. Air is heated directly from sunlight. Solar energy in the form of radiation is absorbed by air molecules, warming the air.
2. The Law of Inverse Squares says that light, radiation, heat are emitted from a source and the amount reaching a destination is inversely proportional to the distance squared between the source and destination. I.e. value at destination = constant / (distance between source and destination)^2
3. Earthshine, or albedo, is the light from the sun which is reflected off the earth. If you are standing on the moon, the earth, at times, appears as a shiny ball due to the reflected light from the sun.

Hope this helps!