Question from MCAT official guide

This forum made possible through the generous support of SDN members, donors, and sponsors. Thank you.


Full Member
10+ Year Member
Jul 22, 2011
Reaction score
Global atmospheric circulation is driven by differences in air T at diff latitudes. Equatorial regions are heated more by the incident sunlight than are polar regions because:

a. earth rotates
b. atmosphere absorbs more sunlight in equatorial regions
c. amnts of greenhouse gases in polar regions are less than in equator
d. sunlight is incident on Earth at smaller angles to the horizontal in the polar regions

Answer is d.

I got this question right because other choices sound stupid.
But, I dont really understand the concept behind this.
How is the incident angle related to heating?

Members don't see this ad.
Shine a flashlight straight at a wall (90 degrees), and you'll get a circle of light maybe a foot in diameter.

Shine a flashlight at a wall at a 45 degree angle and you'll get an oval of light several feet long.

The same energy is being distributed over a much larger angle with a smaller angle of incidence. Therefore there's less energy per square foot of space and less heating per square foot.
  • Like
Reactions: 1 users
Members don't see this ad :)
Hey guys! I see how d is the best answer but isnt b also true? The majority of the sunlight is hitting the equatorial region and thus increasing the atmospheric temperature
The atmosphere doesn't directly absorb a lot of heat, especially as compared to the ground. Remember it's all about the best answer.
It's also about extending scientific reasoning. I would bet that this problem is a "applying scientific principles problem." Think of the sunlight as a force and the earth as an object, and remember w=fdcosthet. Thus the equator has an angle of 0 while the polar regions have some angle, so are not at costheta max.