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, 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. focus(noun) maximum clarity or distinctness of an image rendered by an optical system.