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.
Focus Groups These are excellent research tools. Focus groups are forms of group âinterviewsâ â but there are differences. You will probably be familiar with the term âfocus groupâ from market research reports as they are used often to test reactions to new products or new politicians.