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. Focus groups typically consist of a small group of people consistent with a target market profile that discuss a product or service. Focus groups offer a kind of middle ground between other research methods. They provide a larger sample group than interviews or a case study, while taking advantage of the depth that interviews afford.