User: The greenhouse effect is a result of A. absorption and radiation of energy in the hydrosphere. B. consumption of fruits and vegetables that produce a biofuel. C. absorption and radiation of energy in the atmosphere.
A principal focus or focal point is a special focus: 1  For a lens, or a spherical or parabolic mirror, it is a point onto which collimated light parallel to the axis is focused. Since light can pass through a lens in either direction, a lens has two focal pointsâone on each side.
What is the focal point? A point of focus, or focal point, is defined as the center of interest or activity. Donât take the word center literally, though, as a focal point does not have to be perfectly centered in your frame. In fact, you are encouraged to have it anywhere else for a better composed photographed.