Huygens' principle (first described by the Dutch scientist Christiaan Huygens in 1678) uses geometry to determine the shape of a wavefront at a time t, given some initial wavefront at an earlier time. This can be constructed by imagining that the initial wavefront is a source of wavelets that propagate from each point at the speed of light. From this principle, one can determine the angles of reflection and refraction by considering the speed of light at each point on the wavefront. In this problem, we will explore some of these concepts.

abraham lincoln issued the preliminary emancipation proclamation on september 22nd, 1862. it stipulated that if the southern states did not cease their rebellion by january 1st, 1863, then proclamation would go into effect.

apart from being against desegregation, governor of georgia eugene talmadge opposed as well to the work progress administration, an ambitious program of the "new deal" created by president franklin d. roosevelt to overcome the great depression after world war i. talmadge disagreed with welfare spending, job training and organized labor. according to his ideas, he thought the government was spending too much money on this, and he wasn't willing to accept a wage higher than georgia's lower average wage. besides, talmadge strongly opposed to the "new deal" as he thought it had communist ideas.

no the answer is c only objects touching the earth's surface can be acted upon by an outside force