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.
plural focal points. Learner's definition of FOCAL POINT. [count] 1. : a center of activity, interest, or attention. This port was the focal point of trade two centuries ago. The new school curriculum was the focal point [=focus] of the debate.