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.
Princeton's WordNet(3.00 / 2 votes)Rate this definition: focus, focusing, focussing, focal point, direction, centering(noun) the concentration of attention or energy on something. the focus of activity shifted to molecular biology; he had no direction in his life.