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.
Wiktionary (0.00 / 0 votes) Rate this definition: focus (Noun). a point at which reflected or refracted rays of light converge. The heat of sunlight at the focus of a magnifying glass can easily set dry leaves on fire. focus (Noun). a point of a conic at which rays reflected from a curve or surface converge. focus (Noun).