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.
uk â us â. âº MARKETING, MANAGEMENT a particular way of studying something in order to discover new information about it or understand it better: A focus group is a research method that's typically used to understand a consumer's reaction to a product or service. (Definition of âresearch methodâ from the Cambridge Business English Dictionary Â© Cambridge University Press)