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.
The method employed by him for the purpose is no less simple theoretically than that used for locating the epicentre. A Study of Recent Earthquakes Charles Davison The point of origin is called the centre or seismic focus, and the place on the surface vertically over it the epicentre.